find cute pictures of animals.

Introducing the cute.rb plugin, which adds several commands including !aww, !corgi, !kitty, and !puppy. It's easy to add more by extending the CUTE_IDs and CUTE_SOURCEs arrays with the appropriate command name and imgur subreddit gallery.

It functions by polling the 'top' imgur gallery of a subreddit on the first invocation, and just pops a link + description of an image until it the collection is empty before re-polling.

**Note:** I had to lock the cinch gem in at its current version to avoid everything blowing up when I updated, as the locked version of twitter was too out-of-date.