Adding rspec framework.

Sponsored by Two Red Kites' first open source day!
Adding appraisals gem for testing against multiple versions of Rails.

Sponsored by Two Red Kites' first open source day!
Adding support for subclasses of RenderingController.

This allows for easier customisation of the RenderingController
for additional modules, helper methods, accessors, methods etc.

Sponsored by Two Red Kites' first open source day!