Demo agent get mounts with Puppet

So it will trigger Ruby symbols serialization issues.
Add Ruby symbols serialization integration test
Add Ruby compatible YAML loader

I've got some issues after applying this change, at first glance not
related to this change, but this require more testing and debugging.
Generalize Ruby objects support

Previous commit was supporting only !ruby/object:Puppet::Resource
objects, but that may be useful for any Ruby mapping based object.
Merge pull request #13 from rafaduran/feature/ruby_symbols

Ruby symbols/objects YAML serialization support