Build improvements (cncjs#366)

* Use Node.js 10 to run docker build

* Use webpack-node-externals to exclude node_modules

* Update package dependencies

* Update Dockerfile

* Use Node.js v8 to build docker image

Fix line break issue

Update .travis.yml

Target Node.js v8 for GitHub deployment

Fixed a bug that cannot check for updates

Change placeholder text

Update resource.json

Update styles