Update announcements.json

announcements.json

 [
+	{"id":12,"title":"积分系统测试中","url":"https://github.com/mycard/mycard/wiki/%E7%A7%AF%E5%88%86","created_at":"2013-05-15T18:12:07+08:00","updated_at":"2013-05-15T07:12:08+08:00"},
 	{"id":11,"title":"房间列表白屏或房间密码错误的去玩自动匹配，人太多服务器爆了..", "created_at":"2013-04-27T18:12:07+08:00","updated_at":"2013-04-27T07:12:08+08:00"},
 	{"id":10,"title":"和我签下契约，成为魔法少女吧 (招募开发者/管理员) <-戳我","url":"https://my-card.in/humans", "created_at":"2013-04-13T18:12:07+08:00","updated_at":"2013-04-13T07:12:08+08:00"},
 	{"id":9,"title":"卡组分享系统测试中，有问题或建议请到G+ mycard社群吐槽","url":"https://plus.google.com/communities/112748610591305626436", "created_at":"2013-04-02T18:12:07+08:00","updated_at":"2013-04-02T07:12:08+08:00"},