juiceDocument = function(html, options) {
  return juiceClient.juiceDocument(html, options);
}
Note that makeJuiceClient will take a base object (in this case a function) and enhance it
with a lot of useful properties and functions.

This client adopts cheerio as a DOM parser and adds an "inlineContent" function that let
users to specify the CSS to be inlined instead of extracting it from the html.

The weird "makeJuiceClient" behaviour is there in order to keep backward API compatibility.