Webpack dev server (#902)

* Initial webpack config. Moving to ES6 modules. Some module cleanup.

* WIP

* WIP

* Removing commented out code.

* Removing old deps.

* Removing the build script (used for testing).

* Working tests.

* Switching to node api over cli.

* Updating per comments. Still need to fix server.js to properly run the selenium tests.

* Cleaning up the config.

* More cleanup.

* Bringing back server.js for selenium tests.

* Bringing back old dependencies.

* Adding back eslint rules for webpack config. Final cleanup for webpack config.

* Pointing to correct pre-existing module versions. Adding some extra logic to server.js to ensure it gets transpiled properly.

* Getting make build to work again. Updating package.json with some shortcut scripts.

* Resolving conflict.

* Reverting back to commonjs modules.

* Removing extra spaces in babelrc

contrib/copy-tex/katex2tex.js

@@ -49,4 +49,4 @@ export const katexReplaceWithTex = function(fragment,
     return fragment;
 };
 
-module.exports = katexReplaceWithTex;
+export default katexReplaceWithTex;