A ton of stuff (backbone for multiplayer)

Hello!

This PR adds the following stuff to MathJeweled!

1) Node.JS Server
2) Facebook/Twitter/Local login
3) Redis-backed global leaderboard

Documentation is minimal (only code comments, currently)

This server is the backbone of a multiplayer version of MathJeweled, all that is needed is some logic and a splash of socket.io on the client and server.

This implementation uses Redis and RethinkDB as datastores. RethinkDB, however, could easily be swapped out for MongoDB, etc. If need be.

Thanks,

James