Cleaned up open_session code slightly.
Small cleanup for save_session.
Cleaned up KVSession __init__.
Request new sid_s upon session destruction.
Better docs on cleanup_sessions.
Fix typo in README.rst.
Use introduction directly from README.rst.
Fixed leftover wrong module name.
Automatic expiration if backend supports TTL.
Major documentation overhaul.
Make the example more minimal.
Mention mongoDB in docs.
Section on expiring sessions is much friendlier.
Added tests for redis-backend expiration.