Add a new test setup helper for Adapters.
Create new factory for adapter.base.

This removes the need for every adapter factory to insert an empty
dict at the adapter url.
Stoppable: Add better comments.

Add comments that describe how to use this class. This still
doesn't work with generated documentation, but will do until
I figure out how that works.
Add Spark API.

This is an API for fetching data from Spark Core devices (see
https://www.spark.io/). All devices associated with a given account
will be discovered, along with all variables and functions for each
device.

Updated device descriptions are sent along a channel as they are
discovered.
Add adapter for talking to Spark.IO cloud API.