Install Maven 3.1.0

Related to travis-ci/travis-ci#1324.

**ATTENTION:**

 - wayneeseguin/rvm#2243 should be integrated into RVM `stable` **before merging this PR** (otherwise `rvm::multi` on the Node VM will fail on `rvm install jruby-head`).
 - Chef run_list must be updated (`maven` instead of `maven3`). This is planned to be part of travis-ci/travis-images#4.