Merge branch 'release/v0.4.2' into develop
Add: 增加上下文对话支持 (针对Django)
Add: 增加上下文对话__init__.py
Fix: 修正验证消息NoneType的Bug
Merge branch 'feature/context_django' into develop
Add: 添加登录验证码支持
Fix: 更新WechatExt初始化注释
Fix: 修正登录过程中的验证码结果判断Bug
Fix: 修正django session过期的create错误
Add: 添加在素材库中新建图文消息的方法
Fix: 修正文档语法错误
Merge branch 'feature/ext_news' into develop
Fix: WechatExt中向用户点对点发送视频已更新
Fix: 修正WechatExt中的语法错误
Fix: 修正WechatExt中的Bug
Add VoiceMessage Recognition check default value.

For those empty VoiceMessage, they are useless, but perfectly legal.
Merge branch 'master' of https://github.com/zxygentoo/wechat-python-sdk into zxygentoo-master
Fix: 更新文档
Fix: 更新文档及添加二维码事件支持
Fix: 修正文档细节, 更新异常类文档