Major refactoring (0.2.0)

This PR will lead up to 0.2.0 release. #39

TODO:
- [x] Fix `TODO:s` in code
- [x] Fix pubsub
- [x] Fix pipelines
- [x] Merge gevent PR
- [x] More code cleanup
- [x] Fix all tests
- [x] Clean out `decorators.py`
- [x] More tests for `test_cluster_obj.py`
- [x] Tests for Nodemanager
- [x] Tests for ClusterConnectionPool