Prevent elements to be registered using existing native tag names

According to the spec:

> The custom element type must **not** be one of the following values:
> 
> * annotation-xml
> * color-profile
> * font-face
> * font-face-src
> * font-face-uri
> * font-face-format
> * font-face-name
> * missing-glyph

http://www.w3.org/TR/custom-elements/#concepts