added the ability to print the parse tree

lib/coffee_script/coffee-script.js

@@ -33,6 +33,10 @@
   exports.tokenize = function tokenize(code) {
     return lexer.tokenize(code);
   };
+  // Just the nodes.
+  exports.tree = function tree(code) {
+    return parser.parse(lexer.tokenize(code));
+  };
   //---------- Below this line is obsolete, for the Ruby compiler. ----------------
   // Executes the `coffee` Ruby program to convert from CoffeeScript to JavaScript.
   path = require('path');