Set new Melange version number to 2-1-20130306 in app.yaml.template.

The bump in minor version number from 2.0 to 2.1 is in celebration
of our upgrade to App Engine's Python 2.7 environment. Whee!
diff --git a/app/app.yaml.template b/app/app.yaml.template
index 8d1745b..1fd65d2 100644
--- a/app/app.yaml.template
+++ b/app/app.yaml.template
@@ -15,7 +15,7 @@
 # TODO(proto): uncomment and supply a Google App Engine application instance
 # application: FIXME
 # TODO(release): see the instructions in README about the "version:" field
-version: 2-0-20130304
+version: 2-1-20130306
 runtime: python27
 api_version: 1
 threadsafe: false