Check if browser is supported by web components polyfills

[JosefJezek]

• https://github.com/webcomponents/webcomponentsjs#browser-support
• Provide a mechanism to detect if the user's browser is supported webcomponents/webcomponentsjs#26 (comment)
• http://stackoverflow.com/questions/32965266/how-to-check-if-a-browser-supports-polymer
• https://github.com/DamonOehlman/detect-browser

[indolering]

Move to close, no polyfill does this and there are no good tests one can run to see if it works or not. The only browsers that aren't supported are EOL, literally versions of IE and Safari that can't be updated because the OS support isn't there.