modularized time function, use high resolution timer when available

sub millisecond resolution and a monotonic timing will improve accuracy in simulations, frame timing, etc.

http://updates.html5rocks.com/2012/08/When-milliseconds-are-not-enough-performance-now

I'm not sure how to test this presently as the high rest timer only activates in browsers that support it, and node doesn't. thoughts? happy to submit tests for this.