gauge.go
func (m *CirconusMetrics) RemoveGaugeFunc(metric string) {
	m.gfm.Lock()
	defer m.gfm.Unlock()
	delete(m.gaugeFuncs, metric)
}
func (m *CirconusMetrics) RemoveGaugeFunc(metric string) {
	m.gfm.Lock()
	defer m.gfm.Unlock()
	delete(m.gaugeFuncs, metric)
}
// RemoveGaugeFunc removes a gauge function