Develop a Socrata connector

[EronWright]

Let's develop a connector to read Socrata streams.

Consider using the soda-java library, but be aware that its dependencies are fairly old (jackson 1, jersey 1). We would probably need to shade the dependencies and/or update them.

Alternatively, we could write something from scratch (consumer-side only, to begin with). The River source is written with Spray, which is easy to use. There are quite a few soda model classes (for geo data, timestamps, etc) and query classes that would need to be re-implemented.