Add usage section to README (helm#110)

Similar to
https://github.com/Homebrew/homebrew-core#how-do-i-install-these-formulae

README.md

@@ -5,6 +5,12 @@
 Use this repository to submit official Charts for Kubernetes Helm. Charts are curated application definitions for Kubernetes Helm. For more information about installing and using Helm, see its
 [README.md](https://github.com/kubernetes/helm/tree/master/README.md). To get a quick introduction to Charts see this [chart document](https://github.com/kubernetes/helm/blob/master/docs/charts.md).
 
+## How do I install these charts?
+
+Just `helm install stable/<chart>`. This is the default repository for Helm and is installed by default.
+
+For more information on using Helm, refer to the [Helm's documentation](https://github.com/kubernetes/helm#docs).
+
 ## Chart Format
 
 Take a look at the [alpine example chart](https://github.com/kubernetes/helm/tree/master/docs/examples/alpine) and the [nginx example chart](https://github.com/kubernetes/helm/tree/master/docs/examples/nginx) for reference when you're writing your first few charts.