Remove Growl.framework

I was using a pretty old, outdated version of Growl that's not even
supported anymore. (I'm not sure anyone even really uses Growl anymore,
so there doesn't seem to be any point in keeping it around.)
Don't show notifications pre-10.8

I should probably just drop support for 10.6 and 10.7 (not many people
use those versions of OS X anymore, anyway), but I kind of like the idea
of supporting "antiquated" versions of the OS.
Remove Growl Registration Ticket file

Not necessary, since Growl has been removed.
Merge branch 'no-growl'