fix up comments option

doc/usage.md

@@ -124,7 +124,11 @@ to5.transformFile("filename.js", options, function (err, result) {
   // Optionally replace all 6to5 helper declarations with a referenece to this
   // variable. If set to `true` then the default namespace is used "to5Runtime".
   // Default: false
-  runtime: true
+  runtime: true,
+
+  // Output comments in generated output
+  // Default: true
+  comments: false
 }
 ```