Feature/collaborator generation

Offers to generate an Interface when a specified collaborator does not exist

![generate-collaborator](https://cloud.githubusercontent.com/assets/237866/5288947/8578939a-7b31-11e4-8254-6d575136789c.gif)

This makes me sad but I will comply :-( 

(@stof both spellings are ok in `en_gb` but 'z' is less common, but it has to be 'z' in `en_us`)