fix/mod. remove "data_type" kwarg and default all aggregate types to Python standard FloatType (don't use numpy types).
fix/mod. remove "data_type" kwarg and default all aggregate types to Python standard FloatType (don't use numpy types).

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