Rudimentary rendering of JSON representations

In this commit I included a rather lengthy message to help future
delvers into this code.

In the partial rendering I added the `locals: {json: json}` option.
Without the local `:json` declared, the jbuilder would create a new
BuilderTemplate to render upon completion would dump to the JSON
format. This meant for partials rendered via a non-conventional Rails
manner if partial A rendered partial B then the output of B would be
dumped upon the completion of partial B rendering and then again on
the completion of partial B.

So when I wanted something like this `{"a":{"b":"text"}'` I would
instead end up with `{"a":{\"b\":\"text\"}`

See https://github.com/rails/jbuilder/blob/v1.5.3/lib/jbuilder/jbuilder_template.rb#L114-L115
for more information about the double dumping of data.