Adds a warning about tabs in configuration file (#9586).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@7832 e93f8b46-1217-0410-a6f0-8f06a7374b81

config/configuration.yml.example

@@ -5,6 +5,7 @@
 # Environment specific configuration options override the default ones.
 #
 # Note that this file needs to be a valid YAML file.
+# DO NOT USE TABS! Use 2 spaces instead of tabs for identation.
 #
 # == Outgoing email settings (email_delivery setting)
 #