Initial configuration parser
Adds documentation for the configuration parser and tests
Adds README.md to the configuration package
Refactors configuration parser, removes Registry level from config file

Most conditional parsing code has been moved into UnmarshalYAML
functions for simplicity

Uses the BrianBland fork of goyaml in configuration.go temporarily until
fix https://github.com/go-yaml/yaml/pull/52 is merged in
Merge pull request #652 from BrianBland/configuration

NG: Configuration parser