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/support/jasmine.json

@@ -4,7 +4,6 @@
     "*spec.js"
   ],
   "helpers": [
-    "../node_modules/babel-core/register.js",
     "helper.js"
   ],
   "random": false