Use Rack::Static for assets, bit of refactoring
Addition of generated image to integration spec
Refactored artifacts JSON representation
JS plays nice with new json
Using `Object.create` instead of `new`, much simpler
API now sends generated images that dont have reference images, i.e new screenshots
Returning artifacts as reference paths
Handling generated images (new) now too
Tidied up js
Refactoring
Tidied up project, removed unused stuff
Passed specs

added pollyfill for function#bind as phantomjs doesn't support it by default