Require scikit < 0.20 to allow 0.19.x (#103)

* Require scikit < 0.20 to allow 0.19.x; 0.19.2 in particular seems to be required for OS X + Python 3.7. Test against newer maintenance releases of scikit

* OK, scikit 0.18.1 it is

Bump version to 0.2.3, fix spark-package build #70

Upgraded sbt-spark-package plugin version so the spark-package JAR generated via ./build/sbt spDist works properly. Bump version from 0.2.2 --> 0.2.3 so a new spark-package JAR can be released.

Verified that the spark-package JAR works by QAing on Databricks.

Merge pull request #65 from smurching/spark-2.2-patch

Update README, setup.py for release 0.2.2

readme

Merge pull request #19 from thunterdb/prepare-0.1.2

Changes for 0.1.2 release

Merge pull request #11 from thunterdb/branch-0.1.1-fix2

final fixes to include the README

Merge pull request #8 from jkbradley/pr7-follow-up

Sphinx doc follow-up