Add OSRA Branches

PT Story: https://www.pivotaltracker.com/story/show/77972984

- [x] Added Branch model and seed data
- [x] Added Branch specs and factory
- [x] Added relationship between Sponsor and Branch
I don't see the difference between guarding for nil in booleans  and not other types. If validates presence is enough for other types in the model we can just use the following for booleans in the model and save ourselves the headache as per @sampritipanda original suggestion.

validates :boolean_attribute, inclusion: { in: [true, false] }