Improve documentation on helm installation

The docs were missing the helm dependencies download before running the install, so Postgres was never installed.

Also I'm suggesting the user to download the latest version of helm since executing it with 2.5 failed for me, now with 2.7.2 it works fine.

Documentation/running-clair.md

@@ -44,7 +44,7 @@ A [PostgreSQL 9.4+] database instance is required for all instructions.
 #### Kubernetes (Helm)
 
 If you don't have a local Kubernetes cluster already, check out [minikube].
-This assumes you've already ran `helm init` and you have access to a currently running instance of Tiller.
+This assumes you've already ran `helm init`, you have access to a currently running instance of Tiller and that you are running the latest version of helm.
 
 [minikube]: https://github.com/kubernetes/minikube
 
@@ -53,6 +53,7 @@ git clone https://github.com/coreos/clair
 cd clair/contrib/helm
 cp clair/values.yaml ~/my_custom_values.yaml
 vi ~/my_custom_values.yaml
+helm dependency update clair
 helm install clair -f ~/my_custom_values.yaml
 ```