Update - performance: API `each()` itterator uses `for` loop now

* The native `forEach` is suprisingly slow. I had assumed that it would
  be faster that a for loop, but it appears that due to the function
  execution it is actually much slower. A simple for loop is much better
  for performance and we loose nothing since hte API instance is array
  like.
* This fixes DataTables/DataTables #364