go.talks/present: use moved playground package

R=campoy
CC=golang-dev
https://golang.org/cl/11798043
diff --git a/present/appengine.go b/present/appengine.go
index ae93a5a..1fb2d44 100644
--- a/present/appengine.go
+++ b/present/appengine.go
@@ -7,8 +7,9 @@
 package main
 
 import (
-	_ "code.google.com/p/go.talks/pkg/playground"
 	"code.google.com/p/go.talks/pkg/present"
+
+	_ "code.google.com/p/go.tools/godoc/playground"
 )
 
 var basePath = "./present/"