code: func (h *Host) ServeHTTP(w http.ResponseWriter, r *http.Request) {
  	suffix := httputil.PathSuffix(r)
  	seg := strings.Split(suffix, "/")
  	if suffix == "" || len(seg) == 0 {
  		h.serveImportersRoot(w, r)
  		return
  	}
  	impName := seg[0]
  
  	imp, ok := h.imp[impName]
  	if !ok {
  		http.NotFound(w, r)
  		return
  	}
  
  	if len(seg) == 1 || seg[1] == "" {
  		h.serveImporter(w, r, imp)
  		return
  	}
  	if seg[1] == "callback" {
  		h.serveImporterAcctCallback(w, r, imp)
  		return
  	}
  	acctRef, ok := blob.Parse(seg[1])
  	if !ok {
  		http.NotFound(w, r)
  		return
  	}
  	h.serveImporterAccount(w, r, imp, acctRef)
  }
docs: // ServeHTTP serves:
  //   http://host/importer/
  //   http://host/importer/twitter/
  //   http://host/importer/twitter/callback
  //   http://host/importer/twitter/sha1-abcabcabcabcabc (single account)