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/MongoTransform.spec.js

@@ -1,7 +1,7 @@
 // These tests are unit tests designed to only test transform.js.
 "use strict";
 
-const transform = require('../src/Adapters/Storage/Mongo/MongoTransform');
+const transform = require('../lib/Adapters/Storage/Mongo/MongoTransform');
 const dd = require('deep-diff');
 const mongodb = require('mongodb');