Platform support and scalaz dependency update.

Fair few changes to get it to the point where it builds for 2.9.2, 2.9.3 and 2.10.x:

 - Updated sbt extras script.
 - Increased sbt version to 0.12.3.
 - Increased scalaz version to 7.0.0.
 - Increased default scala version to 2.10.1.
 - Changed cross versions to 2.9.2, 2.9.3 and 2.10.1.
 - Removed CrossVersion.full from scalaz and scalacheck deps.
 - Removed CrossVersion.full from project (matches scalaz, allows for 2.10.x compat)
 - Switch specs version based upon scala version (discussed with Eric T. and this
   is only solution for supporting 2.9.2, 2.9.3 and 2.10.x at the moment).
 - Added tests for multiple scala versions to travis config.

If there is anything that you don't won't in the commit, yell and I will tidy it up.