remove ‘at text’ in message for Tuling and XiaoI

Squashed commit of the following:

commit ccfab5d
Author: Youfou <youfou@qq.com>
Date:   Mon Mar 20 00:57:03 2017 +0800

    add back `except_self` for `Bot.register()`

commit 0eb8725
Merge: e1b5735 99e4cc9
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 23:14:42 2017 +0800

    Merge branch 'develop' of https://github.com/youfou/wxpy into develop

commit e1b5735
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 17:31:18 2017 +0800

    solve conflict

commit 99e4cc9
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 17:31:18 2017 +0800

    solve conflict

commit d503e69
Merge: 396c7a8 5e514fb
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 17:29:41 2017 +0800

    Merge branch 'develop' of https://github.com/youfou/wxpy into develop

    # Conflicts:
    #	docs/faq.rst

commit 396c7a8
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 17:25:52 2017 +0800

    + FAQ

commit 5e514fb
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 17:25:52 2017 +0800

    + FAQ

commit 261e765
Merge: 2b48811 7ed3c2f
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 16:13:53 2017 +0800

    Merge branch 'develop' of https://github.com/youfou/wxpy into develop

commit 2b48811
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 16:12:03 2017 +0800

    update requirements & docs

commit 7ed3c2f
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 16:12:03 2017 +0800

    update requirements & docs

commit 431faae
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 02:30:19 2017 +0800

     + Chat.get_avatar() & Member.remove()

commit 5a9a98a
Author: Youfou <youfou@qq.com>
Date:   Sun Mar 19 00:39:53 2017 +0800

    no need to `bot.start()` now.

    Bot will be started automatically once logged in;
    use embed() instead to block the main thread.

commit 1440f50
Author: Youfou <youfou@qq.com>
Date:   Sat Mar 18 16:25:17 2017 +0800

    update from master branch, and update __version__

commit 3b7f3d6
Merge: a413e21 6bfdbfd
Author: Youfou <youfou@qq.com>
Date:   Sat Mar 18 16:24:19 2017 +0800

    Merge branch 'master' into develop

commit a413e21
Author: Youfou <youfou@qq.com>
Date:   Sat Mar 18 16:23:28 2017 +0800

    Bot.register(senders) => Bot.register(chats)

    相比注册消息的发送者，注册消息所在的聊天对象，更为直观和方便。

update docs

update readme