getElementsByClassName = function getElementsByClassName(container, className, single) {
  if (single) {
    return container.getElementsByClassName(className)[0];
  } else {
    return container.getElementsByClassName(className);
  }
}
A cross-browser implementation of getElementsByClass.
Heavily based on Dustin Diaz's function: http://dustindiaz.com/getelementsbyclass.

Find all elements with class `className` inside `container`.
Use `single = true` to increase performance in older browsers
when only one element is needed.

@param {String} className
@param {Element} container
@param {Boolean} single
@api public