func (m *CirconusMetrics) NewHistogram(metric string) *Histogram {
	m.hm.Lock()
	defer m.hm.Unlock()

	if hist, ok := m.histograms[metric]; ok {
		return hist
	}

	hist := &Histogram{
		name: metric,
		hist: circonusllhist.New(),
	}

	m.histograms[metric] = hist

	return hist
}
func (m *CirconusMetrics) NewHistogram(metric string) *Histogram {
	m.hm.Lock()
	defer m.hm.Unlock()

	if hist, ok := m.histograms[metric]; ok {
		return hist
	}

	hist := &Histogram{
		name: metric,
		hist: circonusllhist.New(),
	}

	m.histograms[metric] = hist

	return hist
}
// NewHistogram returns a histogram instance.