Remove roadrunner

lib/6to5/register.js

@@ -1,7 +1,6 @@
 require("./polyfill");
 
 var sourceMapSupport = require("source-map-support");
-var roadrunner       = require('roadrunner');
 var util             = require("./util");
 var to5              = require("./index");
 var fs               = require("fs");
@@ -129,7 +128,7 @@ module.exports = function (opts) {
 
   if (opts.extensions) hookExtensions(util.arrayify(opts.extensions));
 
-  if (opts.cache) cache = roadrunner.get('6to5');
+  if (opts.cache) cache = opts.cache;
   if (opts.cache === false) cache = null;
 
   _.extend(transformOpts, opts);