Replace __proto__ with modern ways

[mooz]

For now, UxU uses __proto__ pseudo property to achieve inheritance, which is not standardized in current ECMAScript specification (Both 3 and 5).

In draft version of ECMAScript6 specification, __proto__ pseudo property is specified in Annex B. That is, __proto__ implementation is required in web browsers but not required in ECMAScript engine itself.

UxU targets not only web browsers, but also ECMAScript engine itself. To this end, we should replace __proto__ pseudo property with modern ways with Object.create().

[dotnetwise]

I don't recommend that at all.
__proto__ is way faster and it will be standardized in ECMAScript6 anyways.
Beside Object.create is way slower!

This is used on .inheritWith flavor of this library and that is what makes it even faster!

However, make sure you have a fallback to browsers non supporting __proto__ such as IE<=10