Convert backend code to ES modules

Bundling code now with Rollup for its flat bundling and tree shaking
support. Front end code still goes through Webpack for browser support.

lib/common/authorizer.js

@@ -1,11 +1,11 @@
 "use strict";
 
-const validators = {
-  pass: require("./validators/pass"),
-  test: require("./validators/test")
-};
+import pass from "./validators/pass";
+import test from "./validators/test";
 
-class Authorizer {
+const validators = { pass, test };
+
+export default class Authorizer {
   constructor(permissionSets) {
     this.permissionSets = permissionSets;
     this.validatorCache = new WeakMap();
@@ -77,5 +77,3 @@ class Authorizer {
     return validator;
   }
 }
-
-module.exports = Authorizer;