Grid search method must only iterate thru indexes

Hi all,

This is my first pull request, I dont know if I should also send the compiled files (Im sending them), anyway, for the search of the grid, we was iterating thru all object properties, I've just changed to iterate thru the index of the object length, for example in "Ember.js" the old code would give problems because in ember.js a Array has some pre defined properties like (firstObject, lastObject), so even when the array has no items, it was iterating thru those properties throwing exceptions.

Update: also in refreshRanges method we are now iterating by indexes to prevent errors (also more performatic)

Best Regards,

Marius Edelsbrunner