Switch READ-COMMITED so that queries see the last committed data

This should help solving the problem with overlapping bundles

It is what we use in HEY and Basecamp

config/database.yml

@@ -17,6 +17,8 @@ default: &default
   port: <%= ENV.fetch "FIZZY_DB_PORT", 3306 %>
   pool: 50
   timeout: 5000
+  variables:
+    transaction_isolation: READ-COMMITTED
 
 development:
   primary: