Dynamically generate /usr/java/default symlink.

Addresses GitHub PR #16 and #17 where Cloudera has updated the version
of JDK7 that they ship and the hardcoded symlink in cloudera::java5 no
longer works.  We now implement most of the RPM %postinstall that
normally comes with the Oracle JDK as an external shell script.
Change the order of the tags in metadata.json.
Merge branch 'feature/java-default' into develop
Lint: Fix => alignment.
Update to newer Gemfile, Rakefile, and spec_helper.