Set minimal ECMAScript 6
I think we can raise the minimal version to ES6.
It is supported by all current browsers[1] except for IE11 (which is almost no more shipped).
New syntax that we could benefit directly:
- default function parameters
- for/of loop
- properties (rev 584be2585d2a)
- arrow function
- class/super (replace Sao.class_)
- Set
- Promise (replace jQuery.when())
- Array subclassable
I think we can manage to have one patch per topic that review the full code base to upgrade it regarding the topic.
[1] http://kangax.github.io/compat-table/es6/