Update scalatest to 2.2.0

This allowed to simplify libraryDependencies.
Cross-publish for scala 2.10 and 2.11

This also required to update sbt to 0.13 (scala compiler interface
could not be compiled otherwise) and the ls-sbt plugin.

To cross publish just run `+ publish`.
Merge pull request #11 from magro/master

Cross-publish for 2.10 and 2.11