Implemented rescoping with the do keyword.

src/grammar.coffee

@@ -103,6 +103,7 @@ grammar =
     o "Class"
     o "Existence"
     o "Comment"
+    o "Do"
   ]
 
   # An indented block of expressions. Note that the [Rewriter](rewriter.html)
@@ -169,6 +170,10 @@ grammar =
   Existence: [
     o "Expression ?",                           -> new Existence $1
   ]
+  
+  Do: [
+    o "DO Code",                                  -> new Call $2, $2.params
+  ]
 
   # The **Code** node is the function literal. It's defined by an indented block
   # of **Expressions** preceded by a function arrow, with an optional parameter