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
1. 
- If we are using validations the validation will prevent nil from going into the boolean column.
- I don't think booleans are special. I just think because we expect only 2 values it highlights the insidiousness of nils so much clearly. Regardless of the data type, when you issue a select statement against the column in question, null will only ever be highlighted using is null / is not null guards in your statement if nulls are allowed. This is completely different to checking for the presence of an empty value or true / false. Effectively data gets lost as it doesn't turn up in your query.
2. absolutely agree with you but all these things happen pre rails validation / database validation so you will still be unable to put a nil in the boolean column regardless of which method you use.