Do stats on 1st of the month

wiki/src/blueprint/monthly_report.mdwn

@@ -137,6 +137,11 @@ Template
     ===========
 
     XXX: Add the output of `contribute/l10n_tricks/language_statistics.sh`
+    XXX: Add the output of (adjust month!):
+
+        git checkout $(git rev-list -n 1 --before="September 1" origin/master) && \
+        git submodule update --init && \
+        ./wiki/src/contribute/l10n_tricks/language_statistics.sh
 
     Metrics
     =======