Attempting to resolve some unexpected exits

I have noticed gitdocs exiting unexpectedly (more often in OSX than Linux, but happens in both environments) and there few issues opened in relation to this. The exits that I have seen have been from unexpected exceptions in #push_changes, and seem to be scenarios that could be recovered from if the daemon continued running and tried the push again later.

So I have tried to stop #push_changes from raising exceptions by:
* catching StandardError in the #push_changes
* removing the exit command on a bad push

Which I think will resolve some of the unexpected exist. 

Additionally I have also:
* added a notification display unexpected exception
* rescue exceptions from the Guard::Notification messages, just in case

If I have missed any reasons why these exceptions do in fact need to be raised, please let me know and I will continue investigating.