Adds YamlDataStore

This implements data storage as 3 YAML files.  I tested it by hacking the main class and replacing FlatFile with this one, but I will leave the final integration to you.  It works beautifully, but it's not as efficient as it could be because I did not want to work outside this single class until it was proven.

BONUS!
It's recursive, which means theoretically you could have claims with sub claims with sub sub claims with sub sub sub claims... and so on.

Here is what it ends up looking like:
http://pastebin.com/pyVMJxCz

What's missing:
There is no way to import from other DataStore types... yet.  I'll be working on that next.