Notification changes

Hi, welcome to the changelog. I'm going to be using this to document all the updates, improvements, and fixes to lit.salon. Stay tuned.

• Notification changes: You'll now be notified when people you follow post new content (reviews, threads, lists, writings, quotes) and when your own content starts trending.
• Removed notifications: Removed the rather useless notifications: 'user added X book from your shelf or list'