docs(using_helm): change reference from npm to CPAN/Fedora DB

Closes #1271

docs/using_helm.md

@@ -17,7 +17,9 @@ cluster. Think of it like a Homebrew formula or an `apt` or `rpm`
 package for Kubernetes.
 
 A *Repository* is the place where charts can be collected and shared.
-It's like `npm` for Kubernetes packages.
+It's like Perl's [CPAN archive](http://www.cpan.org) or the
+[Fedora Package Database](https://admin.fedoraproject.org/pkgdb/), but for
+Kubernetes packages.
 
 A *Release* is an instance of a chart running in a Kubernetes cluster.
 One chart can often be installed many times into the same cluster. And