mv classList.js polyfill.js
combined all polyfills, now incl. Array.{indexOf,filter,map} and String.trim
added polyfill.min.js, generated with:

curl -X POST -s --data-urlencode 'input@polyfill.js' http://javascript-minifier.com/raw > polyfill.min.js
reduced .length accesses in for loops + used more .push()