Preinstall Scala 2.11.4 and sbt 0.13.5
Preinstall Scala 2.10.2

This is a workaround for sbt/sbt#1439 and lack of Nexus proxy hosted by
Travis infrastructure.
Preinstall Scala 2.9.2 for cross-build purpose

Different 2.9.x versions of Scala are binary incompatible.
Happily, Scala patch versions from 2.10.0 on have become binary
compatible, so we won't have to worry about this point in the future.

See https://github.com/sbt/sbt/issues/1439#issuecomment-52964928
Update changelog
Merge pull request #362 from travis-ci/gc-scala-updates

Scala updates and workarounds