added logic to handle bucket data
added logic to handle bucket data

added generator method `insert_buckets` that handles adding bucket info to metrics

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