Use C-based YAML parser when available

Taken from the top of http://pyyaml.org/wiki/PyYAMLDocumentation

Seems to be about 10× faster.
Merge branch 'master' of github.com:dnephin/PyStaticConfiguration into patch-1
Fix trailing whitespace.
Merge pull request #57 from eevee/patch-1

Use C-based YAML parser when available