Explicitly set java version when compiling twill-examples

Signed-off-by: Terence Yim <terence@continuuity.com>
(TWILL-93) Up the zookeeper timeouts

Zookeeper runs a tad slow on my Macbook Pro, and tests weren't finishing
within the time limits set in the unit tests. This patch ups those limits
so `mvn test` passes.

Signed-off-by: Terence Yim <terence@continuuity.com>
(TWILL-84) Documentation and example enhancements

Fix some maven-javadoc-plugin errors
HelloWorld example should exit if not passed the right arguments
Include twill-examples in the pom modules list
Fix some typos.
Add a .reviewboardrc to simplify submitting patches

Signed-off-by: Terence Yim <terence@continuuity.com>
Fix RAT check failure. Also enable RAT check by default.
Added .travis.yml for CI using Travis-CI.
Enable feature branch travis-ci
Update travis to run with different hadoop version
(TWILL-96) Make YARN unit-tests run on random port.

Signed-off-by: Terence Yim <terence@continuuity.com>
Update travis build command.
Review Comments: Using Timeout (instead of Max attempts) for relaxing constrained provision requests. Modifications for making PlacementPolicy changes compatible with all build profiles (Hadoop version 2.0-2.3).
Resolving conflicts from [incubator-twill] Make YARN unit-tests run on random port. (#9)
Minor fixes in Placement Policy unit tests to make them compatible with all build profiles.