meter: rework meter interface

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

meter/meter_test.go

@@ -0,0 +1,14 @@
+package meter
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNoopMeter(t *testing.T) {
+	meter := NewMeter(Path("/noop"))
+	assert.NotNil(t, meter)
+	assert.Equal(t, "/noop", meter.Options().Path)
+	assert.Implements(t, new(Meter), meter)
+}