Whether Http-Server can specify Content-Type?

**Other information (related issues, suggestions for a fix, etc):**
- Module in lib/http-server.js support config the *content-type* option, but commond in bin/http-server.js doesn't support.
- If using hs to proxy static files which ext is asp, the result will be the download. because the content-type of response is *application/octet-stream*


