README.md in heroku-config-0.3.0 vs README.md in heroku-config-0.4.0

@@ -52,9 +52,22 @@
 
 For more help:
 
     heroku-config aws-rotate-all -h
 
+## Custom Heroku Config Variable Names for AWS Key and Secret
+
+Your app may not be using `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` for the heroku config vars. You can specify the config vars to use with the `--id-key-name` and `--secret-key-name` options. Example:
+
+    heroku-config aws-rotate protected-oasis-24054 --id-key-name AWS_KEY --secret-key-name AWS_SECRET
+
+For the `heroku-config aws-rotate-all` command, use a `:` to separate the app, id key name, and secret key name for the FILE format. Example:
+
+    radiant-fortress-40674
+    protected-oasis-24054:aws_key:aws_secret
+
+Here `radiant-fortress-40674` will use the default `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY`, whereas `protected-oasis-24054` will use `aws_key` and `aws_secret`.
+
 ## Installation
 
 Install with:
 
     gem install heroku-config