Added status system rest api.
Updated status system markdown
Minor change.
Merge pull request #20 from leancloud/status_rest_api

Status rest api
update realtime doc
Merge branch 'master' into wujun_wp
Added status rest api link to rest_api.md
Fixed title.
added graph for signature
Merge branch 'master' of github.com:avoscloud/avoscloud-doc
update peer id constraints
Added more features
Adde x-real-ip to cloud code guide.
Merge branch 'master' into wujun_wp
修改wp8 聊天的文档。