First cut at a gevent connection class.

It seems to kind of work. The integration tests aren't working
right; that needs to be fixed before first. A simple test of the
basic functionality seems to work, but I've not yet tested the
recovery/retry and other execptional conditions.
Remove unused set.
Clean up.
Clean-up and refactor.
Use gevent as default connection class when monkey patched.
Bring back the timeout.
Small cleanup.
Merge branch 'master' into gevent

Conflicts:
	cassandra/cluster.py
	cassandra/connection.py
De-duplicate Connection implementations
Fix failing unit test
Ignore setuptools eggs, too
Use prepared statements for benchmarks
Fix max_compaction_threshold option in metadata
Correctly clear ccm after changing C* version

Conflicts:
	tests/integration/__init__.py
Fix compaction, compression options when generating schemas
Update changelog
Ignore reference errors in the control conn

These frequently happen when the cluster is being shutdown
and the control connection is refreshing the schema or ring topology
Silence control conn errors around shutdown
Update missed unit test
Lowercase boolean literals when generating schemas