Advanced Optimisations

This makes use of the Closure Compiler's `ADVANCED_OPTIMIZATIONS` setting. It reduces the minifed file by 396 bytes (after re-adding the same header comment).

That is ~15% improvement, but I'm not entirely sure it's worth the trouble.

However, from what I've tested, everything works just fine. The browser API methods are not renamed, and the `WOW` constructor and the `init` method are not renamed either. Everything else is.

@matthieua maybe you'll have an opinion.

**TODO:**

- [ ] add back the header comment