change test framework to use files for in and out (s-exp)

test/cases/root/root_module_class.tst

@@ -0,0 +1,12 @@
+module FooBo
+  class Bar
+    a = 5 + foo
+  end
+end
+
+-- -- --
+s(:list,  [s(:module,  "FooBo",  [s(:class,  "Bar",  nil,  [s(:assign, 
+  s(:name,  "a"), 
+  s(:operator,  "+", 
+    s(:int,  5), 
+    s(:name,  "foo")))])])])