Renaming Vool exppressions rightly

Class, Method and Lambda (was block) are expressions.
Just making things clearer, especially for the blocks (ahem, lambdas) is matters.
wip

lib/ruby/class_method_statement.rb

@@ -2,7 +2,7 @@ module Ruby
   class ClassMethodStatement < MethodStatement
 
     def to_vool
-      Vool::ClassMethodStatement.new( @name , @args.dup , @body.to_vool)
+      Vool::ClassMethodExpression.new( @name , @args.dup , @body.to_vool)
     end
 
     def to_s(depth = 0)