Backwards compatibility with Python 2. Fixes #6.

[nh2]

This makes the project compatible with Python 2, so that it works on both Python 2 and 3.

My reason to do this is to make it easier to integrate with projects that still require Python 2, such as nixops.

Achieved via the 3to2 tool:

3to2 --write --nofix=str .

and subsequent run of

find . -type f | xargs unix2dos

because the project right now has Windows line endings everywhere.

[ghost]

Sorry, not interested in supporting Python 2.