Use correct exceptions
Remove not needed method parameters checks

params and headers will never be null as they are set in the
constructor.
Make it easier to debug failing expectations

By printing out everything that is setup for the request, it will be
easier to find what is wrong.

Fixes #163.
Make it easier to debug unexpected requests

By printing out everything that is setup for the requests and
expectations, it will be easier to find what is wrong.

Fixes #163.
Fix tests after improving exceptions messages
Merge pull request #164 from finn-no/improve_output_on_failing_expectations_unexpected_requests

Improve output on failing expectations and unexpected requests