Add a real world example to the docs.

[jackfirth]

Testing with mocks can have lots of subtle cases where it's not clear how to properly use them. A Guide as discussed in #10 would help somewhat, but many approaches are better explained in the context of real code. Therefore, as a complement to the Guide and Reference, there should be some sort of "real world examples" section where the mock package is used to build a real app, small in scope, in a literate-programming fashion. As testing problems naturally occur while developing the app, the study can suggest various mocking approaches and when to use them.

[jackfirth]

Possible name/term: The Mock Walkthrough