Changing KubernetesNamespaceNatsIO to var.

Changes:
    1. Changed KubernetesNamespaceNatsIO to a var.
    2. This will allow a compile time override of nats namespace
    for advanced k8s admins to configure a non nats-io namespace for
    cluster scoped deployment.
    3. Enables workflows referred by #126

pkg/constants/constants.go

@@ -96,7 +96,8 @@ const (
 	NatsBinaryPath = "/gnatsd"
 	// NatsContainerName is the name of the main container.
 	NatsContainerName = "nats"
+)
 
 	// KubernetesNamespaceNatsIO represents the "nats-io" Kubernetes namespace.
-	KubernetesNamespaceNatsIO = "nats-io"
-)
+	var KubernetesNamespaceNatsIO = "nats-io"
+