use built in webpack-dev-server instead of Gulp Webserver for demo task

[thescientist13]

It would be better to remove extra deps (babel for gulpfile, gulpfile.babel.js, gulp, gulp-webserver, etc) and extra files / configuration. Currently the advantage of using this setup is because it easy to spin up after running a webpack production build, which is a key component of the demo task since the production webpack config build doesn't have a webserver configuration. It has the API routing to dev and index.html fallback (needed for SPA's).

Perhaps this just needs an if / else option in the production config?

[thescientist13]

can just use http-server with a proxy option