function shortOut(func) {
  var count = 0,
      lastCalled = 0;
  return function () {
    var stamp = nativeNow(),
        remaining = HOT_SPAN - (stamp - lastCalled);
    lastCalled = stamp;

    if (remaining > 0) {
      if (++count >= HOT_COUNT) {
        return arguments[0];
      }
    } else {
      count = 0;
    }

    return func.apply(undefined, arguments);
  };
}
Creates a function that'll short out and invoke `identity` instead
of `func` when it's called `HOT_COUNT` or more times in `HOT_SPAN`
milliseconds.

@private
@param {Function} func The function to restrict.
@returns {Function} Returns the new shortable function.