My tmux config. I don't know what most of it means anymore. But it works for me.

tmux.conf

# use UTF8
# set -g utf8
# set-window-option -g utf8 on

# make tmux display things in 256 colors
# set -g default-terminal "screen-256color"
set -g default-terminal "xterm-256color"

# set scrollback history to 30000 (30k)
set -g history-limit 30000

# tmux messages are displayed for 1 seconds
set -g display-time 1000

# eliminate command delay for esc in ms
set -sg escape-time 0

# set window and pane index to 1 (0 by default)
set-option -g base-index 1
setw -g pane-base-index 1

# reload ~/.tmux.conf using PREFIX r
bind r source-file ~/.tmux.conf \; display "Reloaded!"

# use PREFIX | to split window horizontally and PREFIX - to split vertically
bind | split-window -h
bind - split-window -v

# rotate to the other layout
bind R select-layout -n

# Bind 'a' to last used window to easily alternate between two windows
bind a last-window

# use " to choose from a list of windows (useful with >10)
bind '"' choose-window

# Make the current window the first window
bind T swap-window -t 1

# Merge the most recent window into a pane on this window
bind m join-pane -d -s !
# Merge the specified window into a pane on this one
bind M command 'join-pane -d -s %%'
# Break a pane off to its own window but keep focus here
bind ! break-pane -d

# Switch to a numbered pane
bind P display-panes \; command-prompt -p index "select-pane -t ':.%%'"

# Switch directly to numbered pane
#bind F1 select-pane -t :.1
#bind F2 select-pane -t :.2
#bind F3 select-pane -t :.3

# map Vi movement keys as pane movement keys
bind h select-pane -L
bind j select-pane -D
bind k select-pane -U
bind l select-pane -R

# and use C-h and C-l to cycle thru panes
bind -r C-h select-window -t :-
bind -r C-l select-window -t :+

# resize panes using PREFIX H, J, K, L
bind H resize-pane -L 5
bind J resize-pane -D 5
bind K resize-pane -U 5
bind L resize-pane -R 5

# C-i for even-vertical arrangement and C-o to zoom current pane
bind-key C-i select-layout even-vertical
bind-key C-v select-layout even-horizontal
bind-key C-o resize-pane -y 1000

# Sync panes
bind C-s set-window-option synchronize-panes

# only constrain size if two sessions are in the same window
#setw -g aggressive-resize on

# mouse control for tmux v2.1
set -g mouse off

# ---------------------
# Copy & Paste
# ---------------------

# Enter copy mode with either the default [ or t
bind t copy-mode

# provide access to the clipboard for pbpaste, pbcopy
# set -g default-command "reattach-to-user-namespace -l $SHELL; cd ."
# set-option -g default-command "reattach-to-user-namespace -l zsh"
set-window-option -g automatic-rename on

# use vim keybindings in copy mode
setw -g mode-keys vi

##### blocking out this section; tmux complains on startup.
# # setup 'v' to begin selection as in Vim
# bind-key -t vi-copy v begin-selection
# # bind-key -t vi-copy y copy-pipe "reattach-to-user-namespace pbcopy"
# bind-key -t vi-copy y copy-pipe "pbcopy"
# 
# # update default binding of 'Enter' to also use copy-pipe
# unbind -t vi-copy Enter
# bind-key -t vi-copy Enter copy-pipe "pbcopy"

bind y run 'tmux save-buffer - | pbcopy '
bind C-y run 'tmux save-buffer - | pbcopy '

# Save entire tmux history to a file - file will be on machine where tmux is
# running
bind-key * command-prompt -p 'save history to filename:' -I '~/tmux.history' 'capture-pane -S -32768 ; save-buffer %1 ; delete-buffer'

# ----------------------
# set some pretty colors
# ----------------------
# set pane colors - hilight the active pane
set-option -g pane-border-fg colour235 #base02
set-option -g pane-active-border-fg colour33 #blue
#set-option -g pane-active-border-fg colour240 #base01

# colorize messages in the command line
set-option -g message-bg black #base02
set-option -g message-fg brightred #orange

# ----------------------
# Status Bar
# -----------------------
set-option -g status on                # turn the status bar on
# set -g status-utf8 on                  # set utf-8 for the status bar
set -g status-interval 5               # set update frequencey (default 15 seconds)
set -g status-justify centre           # center window list for clarity
# set-option -g status-position top    # position the status bar at top of screen

# visual notification of activity in other windows
setw -g monitor-activity on
set -g visual-activity on

# set color for status bar
set-option -g status-bg colour235 #base02
set-option -g status-fg yellow #yellow
set-option -g status-attr dim

# set window list colors - green for active and yellow for inactive
set-window-option -g window-status-fg yellow #base0
set-window-option -g window-status-bg colour236
set-window-option -g window-status-attr dim

set-window-option -g window-status-current-fg brightgreen
set-window-option -g window-status-current-bg colour236
set-window-option -g window-status-current-attr bright

set-window-option -g window-status-last-fg green
set-window-option -g window-status-last-bg colour236
set-window-option -g window-status-last-attr bright

set-window-option -g window-status-format "#{window_index}.#{window_panes}:#W#F"
set-window-option -g window-status-current-format "#{window_index}.#{pane_index}:#W#F"

# Status bar notes:
# #(?client_prefix... highlights the status bar when you hit your tmux control character
# airport -I shows your current wireless network ID
set -g status-left-length 85
set -g status-left "#{?client_prefix,#[bg=blue],}#[fg=green]#h #(/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I | awk -F': ' '/ SSID/{print $2}') "

# show full command name, session name, window & pane number, time, and UTC time
set -g status-right-length 80
set -g status-right "#{?client_prefix,#[bg=blue],}#[fg=cyan]#{=15:pane_title} : #[fg=green]#S #I:#P #[fg=yellow]: %l:%M#[fg=green]|#[fg=yellow]#(date -u +%%H:%%M)"


# older status bar lines I cribbed this stuff from:
#set -g status-left "#[fg=green]: #h : #[fg=brightblue]#(dig +short myip.opendns.com @resolver1.opendns.com) #[fg=yellow]#(ifconfig en0 | grep 'inet ' | awk '{print \"en0 \" $2}') #(ifconfig en1 | grep 'inet ' | awk '{print \"en1 \" $2}') #(ifconfig en3 | grep 'inet ' | awk '{print \"en3 \" $2}') #[fg=red]#(ifconfig tun0 | grep 'inet ' | awk '{print \"vpn \" $2}') #[fg=green]#(/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I | awk -F': ' '/ SSID/{print $2}') "
# set -g status-left "#[fg=green]: #h : #[fg=brightblue]#(curl icanhazip.com) #[fg=yellow]#(ifconfig en0 | grep 'inet ' | awk '{print \"en0 \" $2}') #(ifconfig en1 | grep 'inet ' | awk '{print \"en1 \" $2}') #(ifconfig en3 | grep 'inet ' | awk '{print \"en3 \" $2}') #[fg=red]#(ifconfig tun0 | grep 'inet ' | awk '{print \"vpn \" $2}') #[fg=green]#(/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I | awk -F': ' '/ SSID/{print $2}') "
# set -g status-left "#[fg=green]#h #(/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I | awk -F': ' '/ SSID/{print $2}') #{?client_prefix,#[bg=yellow]#[fg=black]TMUX,    }"