Pep8ify human_time.py and human_time_tests.py

This commit makes the code more pythonic by:
* adhering to PEP8
* removing some ending whitespace
* adding docstrings where they belong in functions (first line in)
* Making comments comments (#) and not strings (""")

Found with flake8 and pylint
Remove whitespace with split & join

split removes sequential and ending whitespace for us