Adds Hiera2 bindings with backends for YAML and JSON

This commit contains the initial work on the Hiear2 bindings producer.
It is W.I.P. at this point as some concepts still remains to be
fully designed. In particular, this commit only contains whats needed
in order to read bindings from one module. The code that finds and
then combines modules is not included.
Merge pull request #29 from thallgren/feature/binder

Adds Hiera2 bindings with backends for YAML and JSON