ES6: Added super test

This checks that:
* super() in the constructor binds to the superclass's constructor
* super.X() in the constructor binds to the superclass's X method
* super() in the X method binds to the superclass's X method
* super is bound statically, and remains bound even when a method is
extracted
WebKit now supports Math.sign and multi-d11g

(d11g = destructuring)
Merge pull request #211 from webbedspace/webkit172711

WebKit now supports Math.sign and multi-destructuring
Corrected #201 and #202

I just noticed that pulls #201 and #202 actually edited the HTML file
instead of the data-es6.js file. This fixes that.
Merge pull request #212 from webbedspace/gh-pages

Corrected #201 and #202
Added note to WeakMap and WeakSet results

WeakMap and WeakSet constructor arguments, such as new WeakSet([obj1,
obj2]), are not supported in most browser platforms.
Added a further note to Map and Set results

Additionally, it seems only Firefox supports arguments to the Map() and
Set() constructors.
Merge pull request #198 from webbedspace/super

ES6: Added super test
Merge pull request #208 from webbedspace/weakmapnote

Added note to WeakMap and WeakSet results
FF34 now supports shorthand methods