isMergeableAtRule = function (node) {
  var isMergeable = false;
  node.forEach(function (item) {
    // TODO Check back when Gonzales updates to fix this
    // Gonzales has issues with nest levels in media queries :(
    if (item.is('atkeyword') && validAtRules.indexOf(item.first('ident').content) !== -1) {
      isMergeable = true;
    }
  });

  return isMergeable;
}
Checks an atRule to see if if it's part of our mergeable at rule list.

@param {object} node - The current node / atRule part of our selector
@returns {boolean} Whether this atRule should be merged or not