function canOverflow(el, axis) {
      var overflowValue = w.getComputedStyle(el, null)['overflow' + axis];

      return overflowValue === 'auto' || overflowValue === 'scroll';
    }
indicates if an element has a scrollable overflow property in the axis
@method canOverflow
@param {Node} el
@param {String} axis
@returns {Boolean}