Echo JS 0.11.0

Polymer is a fully-fledged library that falls back to polyfills when certain features aren't available.
ES2015 classes are not "mandatory", but sugar is... well, sweet. Actually, most of ES6's features could be transpiled to ES5: arrow functions, the spread operator, default arguments, even `let` and `const`. Are those superfluous just for that? No, we're going to use them because achieving the same result with ES5 is just annoying/boring/cumbersome.

Incidentally, `class` is one of those features that can *not* be completely transpiled to ES5. Native elements were just an example, but we also cannot correctly extend `Error` or `Array` with ES5.
Therefore, `class` isn't going away any time soon, and while JavaScript will keep evolving as a functional programming language, for those uncommon cases where classes are needed `class` could and will be used every time they're more convenient than the good old `function` pattern, as long as  we're aware that ES2015's classes aren't anything like "classic" classes.
But then again, every language has its own perks, so as mindful developers we're going to learn the differents like the pros we are.

So far, I had very little use for classes in JavaScript in general (lately I've been using them mainly for React), but things may change.
The next step for classes in JavaScript is defining a way to deal with composition nicely. Nothing is really ready, but the word "trait" is resonating among the community. Let's wait and see.