Higher precision timing labels and better browser compatability

* Use performance-now module which picks the higest precision, most performant
timing option avilable:
performance.now > process.hrtime > Date.now > new Date().getTime()
Timing results are now printed with two decimal places (there doesn't seem to
be any spec available for the console object; FF prints two, while Safari and
Chrome print three)
* Date.now is not available in IE<9 or in older versions of Safari and Opera, so
this change has the added benefit of providing fallbacks for these browsers:
http://kangax.github.io/es5-compat-table/#Date.now