go.talks: fix nobuild_files rule

R=dsymonds
CC=golang-dev
https://golang.org/cl/10830046
diff --git a/app.yaml b/app.yaml
index ace519b..64fe368 100644
--- a/app.yaml
+++ b/app.yaml
@@ -12,4 +12,4 @@
 - url: /.*
   script: _go_app
 
-nobuild_files: ^(?!(present|code.google.com)/)
+nobuild_files: ^((201[0-9]|pkg)/)