Fix issue with git-commit-id-plugin on Travis
[FLINK-1004] Add the maven repositories for all vendors + documentation

This closes #62
Improve error messages for data sinks inside iterations.
[FLINK-1018] Add tests to verify correct placement of pipeline breakers with broadcast variables
[FLINK-1018] Fix cross pipelining/daming info to resolve cross-related streaming deadlocks.
Fix scope for scalatest dependency