Upgrade to Scala 2.11.2

http://www.scala-lang.org/news/2.11.2
Update version of Scala Travis is using
Disable the use of macro paradise for 2.11.x as no longer needed
Merge pull request #145 from ambiata/topic/scala-2.11.2

Upgrade to Scala 2.11.2
Delete TARGET directory for each test/run

This is because repeated runs of recreate-repository resulted in
failures.
Changed snapshot incremental from Reference to Identifier
Changed SnapshotMeta.latest to take a Repository instead of a Reference
Merge pull request #151 from ambiata/topic/reduce-use-of-Reference

Reduce use of Reference for snapshots
SnapshotPlanner rules