code: function userXrd(subject, alias, links, callback) {
      var buffer = '';
  	var context = {
  			subject: subject
  		   ,alias: alias
  		   ,links: links
  	};
  	
  	Mu.compile('userXrd.xml.mu', function (err, parsed) {
  	    if (err) return callback(err);   
  	    Mu.render(parsed, context)
  	      .on('data', function (c) { buffer += c.toString(); })
  	      .on('end', function () {callback(null, buffer);});
  	});
  }
docs: /*
  Generate a user's XRD.
  
  This function simply process the userXrd.xml.mu template and fill-in the subject, alias and links.
  
  @param {String} subject
  the value of the subject item. This should be the acct uri that is being served.
  @param {String} alias
  an alias field. Usually a HTTP URI identifying the same user resource.
  @param {Array} links
  an array of links to be added in the XRD.
  @param {Function} callback
  a callback function in the form function(err, result)
  
  A link has the form:
  var link = {
  "href":	"..",
  "rel" : "..",
  "type": "..",
  "ref" : "..
  }
  
  TODO Allow for more than one alias (array instead of single value)