CRU...D?

I've tested basic adding and retrieval to the local database. I'm not entirely sure we need to delete jokes at this point, so I didn't code that piece. I plan on doing a few more tests but I wanted to get this stuff into the repo, so when I get around to writing the additional tests I'll initiate another pull request. The update method allows a user to change the thumbs up/thumbs down property on a joke.