Removes need to use babel-register (#4865)

* Removes need to use babel-register

- Adds watch to watch changes when running the test to regenerate
- Tests are now pure node 8

* Adds timing to helper.js

* Update contribution guide

* Adds inline sourcemaps generation to restore coverage

* nits

spec/Auth.spec.js

@@ -1,5 +1,5 @@
 describe('Auth', () => {
-  const Auth = require('../src/Auth.js').Auth;
+  const Auth = require('../lib/Auth.js').Auth;
 
   describe('getUserRoles', () => {
     let auth;