Fixes for running postgres on a separate instance

`bundle install` failed during application deployment:

The application deployment does a bundle install. The bundle includes the `pg` gem. The `pg` gem has C extensions. The application may not necessarily run on a system running postgresql (and probably won't). So, make sure that the ruby recipe includes all the right packages to build C extensions in `bundle install`.

**Note:** The postgres recipe in the cookbook wasn't used with RDS. As a later date thing, we should probably make it usable for postgres running anywhere that isn't on the localhost (it assumes localhost now).

`mode 0777`: there's no reason to have mode 777 applied.

database port: the default will be okay but we should support this as an optional setting.