remove fast transformer backwards compatibility

CHANGELOG.md

@@ -16,6 +16,7 @@ _Note: Gaps between patch versions are faulty/broken releases._
  * **Breaking Change**
   * `allowImportExportEverywhere` acorn option has been disabled for spec compliancy so imports and exports can **only** be present at the top level.
   * Caching is now always enabled for the require hook. It also now no longer caches require resolutions.
+  * Optional fast transformer backwards compatibility support has been removed. Use [loose mode](https://6to5.org/docs/usage/loose).
 
 ## 2.12.0
 

lib/6to5/file.js

@@ -78,17 +78,6 @@ File.normaliseOptions = function (opts) {
   opts.optional  = util.arrayify(opts.optional);
   opts.loose     = util.arrayify(opts.loose);
 
-  // todo: remove in 3.0.0
-  _.each({
-    fastForOf: "forOf",
-    classesFastSuper: "classes"
-  }, function (newTransformer, oldTransformer) {
-    if (_.contains(opts.optional, oldTransformer)) {
-      _.pull(opts.optional, oldTransformer);
-      opts.loose.push(newTransformer);
-    }
-  });
-
   _.defaults(opts, {
     moduleRoot: opts.sourceRoot
   });