Making 'Cache array lengths' quicker.

Changed:
for (i = 0, len = arr.length; i < len; i++) {...}

to:
var i = 0, len = arr.length;
for (i = 0, i < len; i++) {...}

It runs A LOT faster. JS Perf test:
http://jsperf.com/browser-diet-cache-array-length/11