http: Add timeout on creation of HttpClient
tests.http: Test creation of HTTP credentials
HTTPClient: Don't decode content

Python 3 string objects don't have a 'decode' method.
Tox: Add Python 3.3 testenv

Python 3.3 is supported by pyrabbit
Merge branch 'add-timeout' of https://github.com/patricksmith/pyrabbit into patrick-merge
Changed default timeout value from 1 second to 5 seconds. Reordered imports