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. 
What do you guys think of:
`validates :code, presence: true, uniqueness: true, numericality: { only_integer: true}, inclusion: 0..99`

Is that overkill? :)