Webpack

Make building static assets for front end easier by automating all the things and splitting them up

- webpack
- gulp
- split into `priv/ui/app` for source and `priv/ui/public` for actual files for running static app
Yup, probably. I haven't really touched the JS with this PR, just copied and pasted it from the monolithic `iodized.js` file into separate module files.

Will need to go back in and add proper error handling. Added that as a task at https://github.com/envato/iodized/issues/15