Use postgres in development

This is an important update, as it will change your configuration a bit; it's easy to get setup though.

Steps:
  1. Update Homebrew:  `$ brew update && brew upgrade && brew doctor`
  2. If everything is OK with the doctor: `brew install postgresql`
  3. Install pg gem:  `ARCHFLAGS="-arch x86_64" gem install pg`
  4.  Decide on how you want to deal with booting postgres. You can have it launch at boot, or you can manually launch it, and to make that easier check out [Lunchy](https://github.com/eddiezane/lunchy).
    - `gem install lunchy`
    - `lunchy start postgresql`