Remove mailcatcher

The mailcatcher gem does not work correctly when executed through Bundler.
Merge pull request #2685 from delynn/patch-2

Remove mailcatcher from bundler plugin
Merge branch 'master' of https://github.com/robbyrussell/oh-my-zsh

* 'master' of https://github.com/robbyrussell/oh-my-zsh:
  Remove mailcatcher