Allow customization of Response classes per resource paths
It's intented to address the following case: https://github.com/gonzalezreal/Overcoat/issues/50

- Use the same logic applied on "modelClassesByResourcePath" to specify how to map responses to different response classes
Update Overcoat.podspec
- Fix an issue on OVCModelResponseSerializer that caused a nil response on every request with error.
- Implement Unit Tests for the new feature (Response classes per Resource Path)
- Fix typo on method comment
Merge pull request #1 from eliasturbay/customization_of_response_class_per_resource_path

Customization of response class per resource path