Adding Linux notification support back in.

This was added a while ago: https://github.com/TrevorBurnham/Jitter/pull/17 but was then (I assume mistakenly?) written over here: https://github.com/TrevorBurnham/Jitter/commit/2d05865537b454c2250ec58054497ea96c4f2d99

I've also added the actual error message into the notification (eg, unexpected indent) and set a 10 second timeout for the notification to disappear (at least with notify-send, I don't know about Growl).

Let me know if this is alright.

Thanks, and cheers for the project!
Matt