Change indentation to 4 spaces as per PEP-8

PEP-8 is a style guide for Python and recommends 4 spaces as
indentation; http://www.python.org/dev/peps/pep-0008/#indentation
Pythonify argument parsing

Just minor restructuring of code to make it more Pythonic.
Merge pull request #7 from plajjan/pep8ify

Pythonify source code a bit