FIX: ensured that in all cases data is returned for a given user.  That is, if no revusions correspond to a given user in a given time period then the data returned indicates this rather than returning nothing (previous behaviour).
FIX: ensured that in all cases data is returned for a given user.  That is, if no revusions correspond to a given user in a given time period then the data returned indicates this rather than returning nothing (previous behaviour).

wikimedia/analytics-user-metrics,rfaulkner/wikipedia_user_metrics,rfaulkner/wikipedia_user_metrics,wikimedia/user_metrics,wikimedia/user_metrics,rfaulkner/wikipedia_user_metrics,wikimedia/user_metrics,wikimedia/analytics-user-metrics,wikimedia/analytics-user-metrics