[custom-elements] Fixed broken Componentizr.customElements method

Description:
  Replaced script injection of polyfill with xhr2 request. Added
  callback to method signature. Updated broken conditionals and object
  detection. Added monkey patch for document.register and
  document.registerElement.
[examples/custom-elements] Added example pages for Custom Elements

Description:
  Added Custom Element base, createCallback, attributeChangedCallback,
  and custom method example with navigation. This is meant to run on a
  server but can work on its own. No CSS has been applyed yet.