Added PyYAML dependency for setting parameters.

Even though there aren't many parameters to juggle here, I love using
YAML. It's by leaps and bounds the best data serialization tool I've
ever used.

You can download PyYAML at BitBucket:
https://bitbucket.org/xi/pyyaml/get/3.10.tar.bz2

I have tested only v3.10 of PyYAML (the most recent tag as of
2013/11/16).
Merge branch 'add_pyyaml' into develop