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.
I would be more explicit in this first step, something like:

~~~ruby
it 'should have a valid Factory' do
  expect(FactoryGirl.build(:sponsor_type)).to be_valid
end
~~~

just to be clear we are testing the validity of the `Factory` rather than the instance