Added two tests cases, which did trigger bugs in an inclusion/exclusion altorithm-based implementation that I did. Especially the to(800) test captures a possible thinking error when implementing a computational solution.
Modified the tests, to make it possible to implement all numbers instead of only 0 and 1, as suggested in the README for the exercise.
Merge branch 'master' of https://github.com/mmakaay/xpython