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. 
We should start using the new [initializers] (https://github.com/AgileVentures/osra/blob/develop/app/models/concerns/initializer.rb). For an example, look at how it was done [here](https://github.com/AgileVentures/osra/blob/develop/app/models/partner.rb).