Helper function to support test runner

Transform test runner for @babel/helper-fixtures module

Babel preset for TypeScript.

Serves a webpack app. Updates the browser on changes.

This is [babel-preset-es2015](http://babeljs.io/docs/plugins/preset-es2015/), minus [modules-commonjs](http://babeljs.io/docs/plugins/transform-es2015-modules-commonjs/), plus [external-helpers](http://babeljs.io/docs/plugins/external-helpers/). Use it wi