Requires `reattach-to-user-namespace` found at https://github.com/ChrisJohnsen/tmux-MacOSX-pasteboard

tmux.conf

set -g default-command "reattach-to-user-namespace -l zsh"
setw -g mode-mouse on
setw -g mouse-select-window on
setw -g mouse-select-pane on
setw -g mouse-resize-pane on
setw -g mode-keys vi

bind-key ` copy-mode
bind-key -t vi-copy 'v' begin-selection
bind-key -t vi-copy 'x' copy-selection
bind-key 'p' run-shell "tmux set-buffer \"$(pbpaste)\"; tmux paste-buffer"
bind-key 'y' send-keys x\; run-shell "reattach-to-user-namespace -l bash -c 'tmux show-buffer | pbcopy'"\; display-message "copied"