Handle case where no items are in a coverage class

Order of comparisons was incorrect, and the case that was trying to be solved (100%, even if num/denom is 0/0) was not handling the edge case of 0/0.
Add test cases for expected behavior

Add test cases for when the denominator is 0, and cases where denominator is less than numerator.
Added strings to test results
Incorrect order on test parameters

assertFoo( "message", expected, actual )
Comment out tests that I don't have a defined behavior

These tests do not have a defined behavior, other than code that has been added over time without concern with invalid data.
Merge pull request #9 from MidLifeXis/fix_empty_coverage_set_results

Handle case where no items are in a coverage class