Add note that quotes around values are not supported. Closes #566

supervisor/skel/sample.conf

@@ -7,6 +7,8 @@
 ;  - Shell expansion ("~" or "$HOME") is not supported.  Environment
 ;    variables can be expanded using this syntax: "%(ENV_HOME)s".
 ;  - Comments must have a leading space: "a=b ;comment" not "a=b;comment".
+;  - Quotes around values are not supported, except in the case of
+;    the environment= options as shown below.
 
 [unix_http_server]
 file=/tmp/supervisor.sock   ; (the path to the socket file)