code: function(matchedWord, imgUrl) {
              if (!imgUrl || !matchedWord) {
                          return;
              }
              var flag = imgUrl.indexOf(options.tag) != -1;	// urls like "img/bg.png?__inline" will be transformed to base64
  //grunt.log.write('urlMatcher :: matchedWord=' + matchedWord + ',imgUrl=' + imgUrl + '\n$$$\n');
  			if((isBase64Path(imgUrl)) || isRemotePath(imgUrl)) {
  				return matchedWord;
  			}
  
  			var absoluteImgUrl = path.resolve(path.dirname(filepath), imgUrl);	// img url relative to project root
  			var newUrl = path.relative(path.dirname(htmlFilepath), absoluteImgUrl);	// img url relative to the html file
  
  			absoluteImgUrl = absoluteImgUrl.replace(/\?.*$/, '');
  
  			if(flag && grunt.file.exists(absoluteImgUrl)) {
  				newUrl = new datauri(absoluteImgUrl);
  			} else {
  				newUrl = newUrl.replace(/\\/g, '/');
  			}
  
  			return matchedWord.replace(imgUrl, newUrl);
  		}
docs: match tokens with "url" in content