Adding an event to key off for package state changes (closes #36)

Not sure if this is the best way to do this but it seemed to be the easiest way for now. This will at least patch the potentially harmful ability to be able to install packages multiple times.
Merge branch 'master' of github.com:bjtitus/settings-view
Using Package Manager events
Forgot theme-install-failed event
Merge pull request #38 from bjtitus/master

Adding an event to listen to for package state changes (closes #36)