Upgrade installation docs

Signed-off-by: Alexander Nesterenko <nestorf250@gmail.com>

docs/helm/helm_install.md

@@ -78,7 +78,7 @@ helm install [CHART] [flags]
 ### Options
 
 ```
-      --atomic                   if set, upgrade process rolls back changes made in case of failed upgrade
+      --atomic                   if set, installation process purges chart on fail
       --ca-file string           verify certificates of HTTPS-enabled servers using this CA bundle
       --cert-file string         identify HTTPS client using this SSL certificate file
       --dep-up                   run helm dependency update before installing the chart
@@ -130,4 +130,4 @@ helm install [CHART] [flags]
 
 * [helm](helm.md)	 - The Helm package manager for Kubernetes.
 
-###### Auto generated by spf13/cobra on 23-Jan-2019
+###### Auto generated by spf13/cobra on 27-Jan-2019