Add Metrics module: pure rrdtool argv builders for ekg samples

test/Main.hs

@@ -6,6 +6,7 @@ import qualified BackoffProp
 import qualified BedroomSpec
 import qualified BusSpec
 import qualified ConnectionSpec
+import qualified MetricsSpec
 import qualified RuntimeSpec
 import qualified SupervisorSpec
 
@@ -15,6 +16,7 @@ main = hspec $ do
   BedroomSpec.spec
   BusSpec.spec
   ConnectionSpec.spec
+  MetricsSpec.spec
   RuntimeSpec.spec
   SupervisorSpec.spec
   BackoffProp.spec