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

test/cases/call_site/call_puts_two.tst

@@ -0,0 +1,7 @@
+puts(3  , a )
+-- -- --
+s(:list,  [s(:call, 
+  s(:name,  "puts"), 
+  s(:arguments, 
+    s(:int,  3), 
+    s(:name,  "a")))])