Organizations CRUD

Adds organizations crud operations according to the user story from PT:
https://www.pivotaltracker.com/story/show/77974308

Accessible on Heroku instance: 
http://sleepy-reef-7794.herokuapp.com/admin/organizations

Implements organizations crud with cucumber tests (similar to the ones for partners) and rspec tests for the model. 
@sampritipanda Can you please explain why you prefer to defer the validation to the db here, when you are so strongly opposed to it elsewhere? Taking `numericality` out of @motasem-salem's code leaves one guessing as to whether the attribute is an integer or a float, necessitating a trip to the schema. Even when @PurityControl and I were recommending to enforce db constraints, we never advocated leaving validations out of the model. The value of a thorough `validates` statement, other than the actual validation, is that it shows at a glance exactly what the attribute has to be.