Update karma_calculator_spec file

My story: https://www.pivotaltracker.com/story/show/82978024
I wrote an it block to make every statement executed al least once. Thus increase coverage of the test. Only the changes to karma_calculator_spec relates to the chores. Other changes I made is my setup attempts and coverage testing on my machines.
you have improved test coverage by touching all parts of the code, but that does not really improve the quality of the tests.

From what I can see in the report, there are the private untouched methods `profile_completeness`, `membership_length` and `activity`. There is a great talk by Sandi Metz on how to approach testing `private` methods https://www.youtube.com/watch?v=URSWYvyc42M. If you have 30 minutes to spare, I highly recommend watching that video. The **TL;DR** is, private methods should be implicitly tested from the public interface. This file is missing tests for membership activity, profile completeness and membership length. In fact, what’s worrying is that the current tests supposedly test the membership length :worried: