Adds nokogiri for HTML parsing.
Removes obsolete text.
Adds API models.

Adds Lextran model namespace with Route, Stop, and Arrival models.
Each of these can query the Lextran API for new data.

Arrivals currently don't work. The Lextran bus stop endpoint requires
a referrer and a session in which the user has previously picked
a route. This will be awkward to do on the server.
Lots of changes. Some stuff working.

- Adds controller logic for refreshing DB as necessary.
- Adds controller actions.
- Adds scopes to models.
- Adds API interaction (working: routes, stops; broken: arrivals).
- Cleans up JSON through serializers.
- Fixes routes to be nested.
- Updates README to reflect current status.

Still no tests. =((