Fixed sbt build definition and bumbed Scala version to 2.9.2

Moving to Sbt 0.12.1 (previous commit), caused the project to fail
buid. Apparently, the former build definition was relying on un-specd
Sbt's behavior.
Bumped mima version to 0.1.4
Merge pull request #25 from dotta/prepare-release

Prepared 0.1.4 release
Bumped version number to 0.1.5-SNAPSHOT
Inadvertently removed URL to scalasbt.artifactoryonline in previous commit