Replace Oracle JDK 7 with OpenJDK 7.
Replace Oracle JDK 7 with OpenJDK 7.

Oracle JDK 7 is no longer supported on Travis CI; more details in:
https://github.com/cloudera/director-google-plugin/pull/137#issuecomment-329897557

Cloudera decided to replace Oracle JDK 7 with OpenJDK 7:
https://github.com/cloudera/director-google-plugin/pull/137#issuecomment-347349558

Also, added `dist: trusty` and `sudo: false` parameters to use the
latest available distro version and lighter-weight container-based
builds.

cloudera/director-google-plugin,cloudera/director-google-plugin