[ruby mode] Add fold info

Author: francocatena

mode/ruby/ruby.js

@@ -286,7 +286,8 @@ CodeMirror.defineMode("ruby", function(config) {
     },
 
     electricInput: /^\s*(?:end|rescue|elsif|else|\})$/,
-    lineComment: "#"
+    lineComment: "#",
+    fold: "indent"
   };
 });