Initialize MetricAggregator in NewMetricAggregator instead of Aggregate
Initialize MetricAggregator in NewMetricAggregator instead of Aggregate

tiedotguy/gostatsd,tiedotguy/gostatsd,jmptrader/gostatsd,atlassian/gostatsd,aelse/gostatsd,atlassian/gostatsd,DeanThompson/gostatsd,kisielk/gostatsd,aelse/gostatsd