Switch to Mongo/Mongoose

* Update User model/API routes/auth
* Update checkDatabase
* Uninstall rethinkdb/thinky, add mongoose
Docs update

Switch to Mongo, nix protobuff req, fix line about devserve
Merge branch 'master' of https://github.com/asm-products/buckets into mongo
Add testing and CI

- Use mocha and chai for both client and server.
- Start to set up testem to test client on multiple browsers.
- Set up travis ci