Simd.js support

[bnolan]

With simd.js support getting closer to released browsers, it might be worth investigating what parts of cannon can benefit from SIMD instructions.

https://blog.mozilla.org/javascript/2015/03/10/state-of-simd-js-performance-in-firefox/

[joates]

+1

@schteppe how do you feel about branching the codebase so that you can accept PRs & run some benchmarks while this is a draft specification ?
(without adversely affecting the current stable build)

[schteppe]

Sounds cool! I made a new branch for SIMD.js stuff: https://github.com/schteppe/cannon.js/tree/simd

Some thoughts from me:

• Can we keep compatibility with non-SIMD browsers?
• Will we need to change the API much?
• Benchmarks can be done with benchmark.js. Or is there something better?

[bnolan]

We can use a polyfill to emulate SIMD in non-compatible browsers (hopefully if it's implemented well using float32arrays it'll still be just as fast), and it might be helpful porting some of cannon to use array buffers anyway!

[bnolan]

I think we should endeavour to not change the API at all, the cannon api is great fun to use. :)