集成已有用户体系
Merge branch 'master' of https://github.com/easemob/developer.easemob.com

# By dujiepeng (3) and zhanw (2)
# Via zhanw
* 'master' of https://github.com/easemob/developer.easemob.com:
  update contactmanager.md
  add contactmanager.md
  update.
  更新文档
  update.