soften the recommendation of hypens in chart names

We definitely still suggest that dashes are acceptable for chart packages, but users should be aware of the limitations of dashes in variable names in Go templates.

docs/chart_best_practices/conventions.md

@@ -4,19 +4,21 @@ This part of the Best Practices Guide explains general conventions.
 
 ## Chart Names
 
-Chart names should be lower case letters and numbers. Dashes (-) are not allowed:
+Chart names should use lower case letters and numbers, and start with a letter.
 
-Examples:
+Hyphens (-) are allowed, but are known to be a little trickier to work with in Helm templates (see [issue #2192](https://github.com/helm/helm/issues/2192) for more information).
+
+Here are a few examples of good chart names from the [Helm Community Charts](https://github.com/helm/charts):
 
 ```
 drupal
-cluster01
-aws-cluster-autoscaler #incorrect do not use dashes in the name
+cert-manager
+oauth2-proxy
 ```
 
 Neither uppercase letters nor underscores should be used in chart names. Dots should not be used in chart names.
 
-The directory that contains a chart MUST have the same name as the chart. Thus, the chart `nginx-lego` MUST be created in a directory called `nginx-lego/`. This is not merely a stylistic detail, but a requirement of the Helm Chart format.
+The directory that contains a chart MUST have the same name as the chart. Thus, the chart `cert-manager` MUST be created in a directory called `cert-manager/`. This is not merely a stylistic detail, but a requirement of the Helm Chart format.
 
 ## Version Numbers