Install oh-my-zsh my way...

ohz.sh

#!/bin/bash

os=`uname`

if [[ "$os" == 'Linux' ]]; then
    sudo apt-get install zsh zsh-common
    chsh -s /bin/zsh
elif [[ "$os" == 'Darwin' ]]; then
    brew install zsh
    chsh -s /usr/local/bin/zsh
fi

wget https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh -O - | sh

cp ~/.zshrc ~/.zshrcbk

sed -e 's/^\(ZSH_THEME="\)[^"]*/\1agnoster/' \
    -e 's/^\(plugins=(\)[^)]*/\1git utility ruby syntax-highlighting history common-aliases cpanm dirhistory gem pip python rvm/' \
    -e 's/^\(export PATH="\)\($PATH:\)\?/\1$PATH:/' \
    -e 's/$PATH$PATH/$PATH/' ~/.zshrcbk >~/.zshrc
if [[ "$os" == 'Darwin' ]]; then
    sed -e 's/^\(plugins=.*[^)]\)/\1 osx/' ~/.zshrc
fi

Run using wget https://gist.githubusercontent.com/retrography/955578106208022b222e/raw -O - | bash