Previously, if rbt was used to fetch a a response that was not

encoded with ASCII, writing to the SQLite database would cause it to

crash due to trying to insert binary data into a text field. The API

cache now stores the response body as a binary blob. The caching layer

no longer has to worry about the encoding or data type of the data

being cached.
Because of the schema change, update API Cache schema to version 2.
Use unicode literals in api/cache.py.

Unit tests passed.
Posted and updated this review request with the patch.
Caching an HTTP response that is not ASCII encoded no longer causes

rbt to crash.