Support for delete a file

[hultberg]

Ref: https://stackoverflow.com/questions/16678661/how-can-i-delete-the-current-file-in-vim

A nice-to-have feature. I'm thinking we should implement an own command for this, like :del [path] or :rm [path] and call on atom deleting handling. One thing to think about is if we should somehow ask for confirm of an deletion. However, as atom just moves the files into the trash, the user has the ability to undo the action.