This is a renderer which currently just looks for fitting templates
based on the name and accept type. The accept type can be mapped in the
accept class to make it easier to work with.
This should replace Rack::Request in the hole lib. It seperates
everything worth into its own classes, like parameters and the accept
header till now.
More will follow
The intention is, that everything gets rendered first and after that
packed to a response. This way, error checking on the response can be
done after rendering.