Mention js-es5, and move js-flatten down to optimization section.
Mention js-es5, and move js-flatten down to optimization section.

It's not really a feature.

pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe