Possible Upload workaround (based on OCMock)

I have been able to implement mock tests for my upload requests based on [this Stackoverflow answer](https://stackoverflow.com/a/20663781/5098984).

As a result, I have removed every `OHHttpStubs` dependency from my project, to not mix libraries. Maybe you could change your internal approach to stubbing the web requests and support upload tasks as well, based on `OCMock`?

If you do not want to depend on an external library, I think you could implement similar behaviour as `OCMock` with **Method Swizzling**.