Added sf Symfony2 binary alias

plugins/symfony2/symfony2.plugin.zsh

@@ -11,7 +11,9 @@ _symfony2 () {
 }
 
 compdef _symfony2 app/console
+compdef _symfony2 sf
 
 #Alias
 alias sf2='php app/console'
-alias sf2clear='php app/console cache:clear'
+alias sf2clear='php app/console cache:clear'
+