support running on the mac with shells besides just bash

[devoncarew]

like zsh :)

[devoncarew]

It looks like atom may be running in bash as is? And the launched processes seem to have the right path set up. So we may not need to do our bash trampolining thing.

[devoncarew]

Look into whether we can detect the current shell using $SHELL. If bash, just shell out. If zsh, the same. If csh, how do we detect which shell the user normally uses? (the Dock launches processes in the csh, not whatever the user's default shell is)

[ianloic]

I have most of a patch working...