Add support for JDBC connector.

Modify params.pp to abstract the package name for the postgresql JDBC
connector and add Class['postgresql::java'].  Also update the README.md
to mention the availability of this class.
Add rspec test for Class['postgresql::java'].

This test conforms to the rspec-puppet and puppetlabs_spec_helper
standards.
Clean up java.pp manifest documentation.

Also clarify postgresql::java rspec test.
Merge pull request #116 from razorsedge/feature/jdbc

Thanks for your patience while we were sorting out the repo organization issues!