Tweetstream

- Added "raw" kwarg to stream classes. Returns raw tweets rather than
decoding the JSON.

- New, fine grained, disconnect exceptions. Adds a ReconnectableError
of which there are three subclases for different reconnect behaviours.

- Fixed issue 16. Odd case where python_version_tuple was returning ints
rather than the strings the docs promis. Make sure we always cast to int.

- Fixed issues 2 and 12, related to low volume streams not yielding tweets
until a relatively large buffer was filled. This meant that tweets would
arrive in bunches, not immediatly.
- Switched to HTTPS urls for streams. Twitter will switch off HTTP streams
on 29. sept. 2011.
- Added support for Python 3

- Changed API to match latest twitter endpoints. This adds SampleStream and
FilterStream and deprecates TweetStream, FollowStream, LocationStream,
TrackStream and ReconnectingTweetStream.

- Added LocationStream class for filtering on location bounding boxes.

- Removed a spurious print statement left over from debugging
- Introduced common base class for all tweetstream exceptions
- Make sure we raise a sensible error on 404. Include url in desc of that error