tmux: zsh: Remove reattach-to-user-namespace from default-command

and set reattach-to-user-namespace in osx $EDITOR (subl --wait)
[tmux-MacOSX-pasteboard/Usage.md at master · ChrisJohnsen/tmux-MacOSX-pasteboard](https://github.com/ChrisJohnsen/tmux-MacOSX-pasteboard/blob/master/Usage.md)
Fix using single quote