Reply with "201 Created" status when publishing + patch

[yirkha]

From HTTP/1.1 RFC2616: "If a resource has been created on the origin server, the response SHOULD be 201 (Created)." This also seems to be a common behavior on REST interfaces, and the original ngx_http_push_module did this.

A patch is available here: https://gist.github.com/yirkha/6354891