Change how renderer output is converted to JSON
Change how renderer output is converted to JSON

Update the railtie to fix issues with the way renderer output is
converted into a JSON string in the controller.

Cached and non-cached resources need slightly different handling, so
make a logical check to tell the difference and use the appropriate
method.

jsonapi-rb/jsonapi-rails,jsonapi-rb/jsonapi-rails,jsonapi-rb/jsonapi-rails