cleanup & refactor

Cleanup all the things. Major changes include:

*  <code>databases::postgresql</code> hates the way we install pg93, so hack around it
*  use yum_repository
*  use encrypted data bags
This functionality is actually included in the postgres cookbook. You just need to enable the ``node['postgresql']['enable_pgdg_yum']`` attribute to do it. I'd rather not import postgres specific stuff in this cookbook if its already done in the upstream cookbook.