function shallowMerge(o1, o2) {
  var o = {},
      k;

  for (k in o1) o[k] = o1[k];
  for (k in o2) o[k] = o2[k];

  return o;
}
A simple helper to shallowly merge two objects. The second one will "win"
over the first one.

@param  {object}  o1 First target object.
@param  {object}  o2 Second target object.
@return {object}     Returns the merged object.