refer :
http://stackoverflow.com/questions/10906411/asp-net-web-api-put-delete-verbs-not-allowed-iis-8
http://www.inmotionhosting.com/support/community-support/website/put-and-delete-request-methods-blocked
有些hosting公司似乎会protect这个, 可以通过 web.config remove WebDAVModule 来解决.
