added docs for $dollar
added the docs for log_empty_request
added English docs of error_page
fixed the docs with shudu's review comment.
added lua module documentaion
added directive documentaion of 'log_escape'
added lua module version
added docs of variable $conn_requests
added docs of 'server_admin', 'server_tag', 'server_info'
fixed the missing div tag
added the docs of $sent_cookie_
added the docs for TFS module
noted that Tengine is a community effort
Merge pull request #35 from yaoweibin/update_0204

Update 0204
Merge pull request #31 from yaoweibin/update_1227

Update 1227
Merge pull request #38 from zhuzhaoyuan/index-developed-by

noted that Tengine is a community effort
Update core.html
Update http_log.html
Merge branch 'master' of git://github.com/alibaba/tengine-website into update_0717

Conflicts:
	document/variables.html
	document_cn/variables_cn.html
Merge remote-tracking branch 'yaoweibin/update_0717' into update_0717