Improve output formatting when JSON comparison fails in assertions

[steinfletcher]

Given that an defined expectation does not match the test output, e.g. the json body response does not match the value returned by the application under test, it is difficult to identity which fields do not match.

Implement a solution that makes it easy to identity which parts of the json did not match. See testify for an example.

[steinfletcher]

I am picking this up.