Set MAVEN_OPTS for Travis-CI
Set MAVEN_OPTS for Travis-CI

Travis builds occasionally fail with Java heap space error.

This commit sets higher limits to fix the issue mentioned above.

Reviewers: Lior Zeno, Mike Percy

This closes #75

szaboferee/flume,tmgstevens/flume,iaiengxia/flume,tmgstevens/flume,tinawenqiao/flume,tinawenqiao/flume,tmgstevens/flume,szaboferee/flume,tinawenqiao/flume,szaboferee/flume,iaiengxia/flume,tinawenqiao/flume,tmgstevens/flume,szaboferee/flume,iaiengxia/flume,iaiengxia/flume