Compile with jdk8 on Travis CI
Compile with jdk8 on Travis CI

This commit changes the Travis CI build config to use Java 8.

This closes #142.

Reviewers: Denes Arvay

(Attila Simon via Denes Arvay)

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