Upgrade to Spark 0.9.1 / SBT 0.13.1, some other goodies

This pull request includes:
- Upgrading to Spark 0.9.1, SBT 0.13.1, and Scala 2.10.4
- Adding [scoverage](http://github.com/scoverage) code coverage
- Adding the ability to publish jars via bintray (thus resolving issue #3 )
- Adding automatic scalastyle checks during compile