Function mixin

fastdom.js:230–234

* Mixin own properties of source * object into the target. * * @param {Object} target * @param {Object} source

(target, source)

 * @param  {Object} source
 */
function mixin(target, source) {
  for (var key in source) {
    if (source.hasOwnProperty(key)) target[key] = source[key];
  }
}

// There should never be more than
// one instance of `FastDom` in an app