bug-fix when user don't have web components pollyfill, gets an error (#131)

* bug-fix when user don't have web components pollyfill, gets an error

* added message for users that don't have web component polyfill loaded on console

* applied the changes on reveal.umd as well

* updated warning message

* reordering the logic a bit so we can exit if window.WebComponents is not found

* adding built files

* updating logic for polyfill being present or not

Author: Homa