Added YAML config support.

- Manifest format parsing is now checked by the file extension ie: .json, .yml or .yaml.
- load_yaml in common/tools is the same as the json version.
- schema checking of manifest still passes (and fails appropriately) like the json manifests.
- I've also included a sample yaml config based off of the debian test json manifest.
Fixed import style.
Added pyyaml to setup.py.
Fixed formatting standards on files I've changed.

Used command `find . -name '*.py' | grep -v minify_json | xargs pep8 --ignore=E101,E221,E241,E501,W191`
Merge pull request #69 from Rory-Finnegan/development

YAML config support