compare_perf_test.py is now covered with unit tests and public methods are documented in the implementation.
Minor refactoring to better conform to Python conventions:
* classes declared in new style
* proper private method prefix of single underscore
* replacing map with list comprehension where it was clearer
Unit test are executed as part of validation-test.
.gitignore was modified to ignore .coverage and htmlcov artifacts generated by the coverage.py package
