changed setup.py to break out protocol versions for sentry as an 'extra' dependency
updated docs to reflect that you will need to specify the protocol version when installing heka-py-raven
bumped revision to 0.7
updated testcases and requirements file
fixed an incomplete comment in setup.py
Merge pull request #3 from mozilla-services/features/sentry_protocol_versions

separates dependency on raven as an 'extra' to isolate sentry protocol versions