tmux-session save & restore
https://github.com/mislav/dotfiles/blob/d2af5900fce38238d1202aa43e7332b20add6205/bin/tmux-session
change prefix to ctrl+s since we use ctrl+a in terminal to move to the beginning
indentLine slow things down. Change to forked Ag instead of Ack
variable should be prepend with `$`. Shame on me.
still half-way to fix tmux compability with Linux & OS X