Implement factory girl

Pivotal Tracker story Switch to FactoryGirl: https://www.pivotaltracker.com/story/show/75757844.
- add factory_girl_rails gem
- create factories for partners, provinces, sponsor_types, sponsors, statuses
- create model spec for sponsor_type using sponsor_types factory

All factories confirmed to create valid objects.
@sampritipanda 
- `it` on line 8 refers to the `subject`, and I thought that the `it`s within `context` blocks did too, but now realize that they don't
- with `context`, I've been following the guidelines from [betterspecs.org](http://betterspecs.org/#contexts)
- & @yggie I had tried the `it { is_expected.to ... }` syntax before but it fails with `NameError: undefined local variable or method`. Because we are on rspec v2.14?