Pulled in updates from Opscode's cookbook and completely removed database dependency.

I made a few updates to this cookbook:

* Pulled in recent changes made to Opscode's official `postgresql` cookbook
* completely removed the dependency on the `database` cookbook; this mainly affects the `setup` recipe; adding users and databases is done with the `psql` command instead of the resources that were previously available from the `database` cookbook.

This has only been tested on Ubuntu 12.04, and I think will address Issues #2 and #3;  This pull request will also supercede #4.

Let me know if you'd prefer to pull this into a separate branch so you can test on 10.04!  :banana: