Stable vs dev install messaging, ref roots/docs#140 [ci skip]

Author: retlehs

README.md

@@ -34,6 +34,12 @@ Install Sage using Composer from your WordPress themes directory (replace `your-
 
 ```shell
 # @ app/themes/ or wp-content/themes/
+$ composer create-project roots/sage your-theme-name
+```
+
+To install the latest development version of Sage, add `dev-master` to the end of the command:
+
+```shell
 $ composer create-project roots/sage your-theme-name dev-master
 ```