Scikit-spark

- scikit-learn 0.22 support added

- scikit-learn 0.21 support added
- scikit-learn 0.21 dropped support for Python 2 and that is mirrored in scikit-spark

- scikit-learn 0.20 support added
- Automated testing with travis setup

- Tested with real data
- Fixed bug where you couldn't pickle an RS or GS object more than once
- https://github.com/scikit-spark/scikit-spark/issues/6
- Made RS and GS work without Spark and added a test
- Made the `spark` argument work with boolean values
- Added `spark` argument to the docstrings

- Tests run in Python 2 and Python 3 now
- Fixed README example (not enough parameters for RS to try)

- Fixed setup.py import for skspark