New Article: Introduction to Custom Elements

Hi all,

I have drafted the latest article "Introduction to Custom Elements".
Could you kindly review this?

Thanks.
typo (webcomponenTs). Also: 
1) if folks bower-install it, it'll be in bower_components/webcomponentsjs/webcomponents.js. Not sure if it's worth using that path or if you think most people will get it some other way.  
2) should probably use the minified version.
3) Might be worth mentioning that the polyfill should be the first script on the page -- or at least before other scripts that manipulate DOM. (This may not be a problem if they're only using custom elements, I think this mainly affects the shadow DOM polyfill.)
4) But ignore #3 if you link to the wc.org polyfill page.