Fix for https://code.google.com/p/mock/issues/detail?id=203

This fix ensures that tests decorated with @mock.patch keep their names in the py.test output.

I've got an integration test that combines mock.patch and pytest here:

https://github.com/burrowsa/pytest_mock_integration_test

While I'm not sure that the test is a good candidate for adding to pytest (as it depends on mock) it does show the problem is solved by this fix.

Note: I had to monkey around a bit to get the tests for this pull request to run in travis - hence the extra commits