The reason for the factory was that the HttpInterceptor should be a clean implementation of a HTTP Interceptor, used by $http. We'd rather not mix other functionality into it, such as detecting/deciding if a api mock should be used or not.

There's also a use-case where you want to know if the API is being mocked, so you can include `mockSwitch` instead of including a HTTP Interceptor in your Controller. There's probably another way to do this but it should be separate from the interceptor.