when retrieving the mailbox list, support children that may come before their parents

closes #163

lib/imap.js

@@ -465,7 +465,8 @@ ImapConnection.prototype.connect = function(loginCb) {
                 }
                 box.parent = parent;
               }
-              if (!curChildren[name])
+              if (curChildren[name])
+                box.children = curChildren[name].children;
               curChildren[name] = box;
             }
             break;