Fix test for new requests version.

The "read" method signature of the urllib3 response has changed.
We wrap our StringIO in the tests so that it matches the signature.
Disable requests logging. Fixes #2

The urllib3 package in the requests module logs every request on INFO level.
Since this is cluttering our logs and the github-watchlist does also log
on INFO level we change the log-level for urllib3 to WARNING.