build UMD bundle and polyfill language features

.eslintrc.yml

@@ -15,11 +15,6 @@ rules:
   strict:
     - error
     - safe
-  # disallow Object.assign
-  no-restricted-properties:
-    - error
-    - object: 'Object'
-      property: 'assign'
 overrides:
   - files:
       - 'docs/js/**/*.js'

.travis.yml

@@ -49,7 +49,7 @@ jobs:
       node_js: '10'
       name: 'Node.js v10'
 
-    - script: npm start test.bundle test.browser
+    - script: npm start test.browser
       name: 'Browser'
       node_js: 12
       install: npm ci # we need the native modules here

browser-entry.js

@@ -210,10 +210,10 @@ Mocha.process = process;
  * Expose mocha.
  */
 
-global.Mocha = Mocha;
-global.mocha = mocha;
+mocha.Mocha = Mocha;
+mocha.mocha = mocha;
 
 // this allows test/acceptance/required-tokens.js to pass; thus,
 // you can now do `const describe = require('mocha').describe` in a
 // browser context (assuming browserification).  should fix #880
-module.exports = global;
+module.exports = Object.assign(mocha, global);