Modified wp post edit command to allow non-default GUI editor 

1. Replaced the launch_editor_for_input function in php/utils.php

Now the terminal sits and waits for any changes to be made to the temp file. When it detects a change, it automatically updates the post.

2. Got rid of true/false checking in php/commands/post.php

If there's no change to the tmpfile, then the user can just abort the wait, and no update takes place.

I'm not sure how this behaves with the built-in vim or emacs, I haven't tested those.

Also this is my first ever pull request on github so please pardon me if I made and mistakes.