2015-02.py: Clean up, add tests, add docstrings
2015-02.py: Clean up, add tests, add docstrings

robjwells/adventofcode-solutions,robjwells/adventofcode-solutions,robjwells/adventofcode-solutions,robjwells/adventofcode-solutions,robjwells/adventofcode-solutions,robjwells/adventofcode-solutions