fix slow terminal init

Moved all completion.sh and .zsh files into the zsh directory, so I
don't end up scanning all of my dotfiles plus nvm each time a new
terminal is initialized.

tmux/aliases.zsh

@@ -1,4 +0,0 @@
-alias ta='tmux attach'
-alias tls='tmux ls'
-alias tat='tmux attach -t'
-alias tns='tmux new-session -s'