Update README

Switch to github.com for source of httpbuf, thegoods.biz is not firewall
friendly because it refers people to the git:// URL

web/server.go

@@ -5,12 +5,12 @@ package web
 
 import (
 	"fmt"
+	"github.com/goods/httpbuf"
 	"github.com/gorilla/mux"
 	"github.com/gorilla/sessions"
 	"github.com/jhillyerd/inbucket/config"
 	"github.com/jhillyerd/inbucket/log"
 	"net/http"
-	"thegoods.biz/httpbuf"
 	"time"
 )