updates to webpack4

[christopher-johnson]

closes #76

• also updates babel and eslint packages to work with new webpack4 api
• babel-preset-react-app includes both preset-env and preset-react(among others) as a bundle.
• mixing import and module.exports is no longer allowed in an ES6 module. (ref changes in index.js)
• includes required linting changes to pass build and tests. Most are react/destructuring-assignment
• adds "no-console": "off" rule to .eslintrc as console log statements are typical with node.
• adds paths.js which includes path resolvers and aliases for scripts.
• adds NODE_ENV to script defs in package.json.

[christopher-johnson]

about the dev mode and dev server in the start script, this still needs some work. It is fairly typical to have a separate webpack config for development and the dev server, and this can be done in another PR.

currently, the start script has an extra NODE_ENV=development that does nothing in the initial build since it is overridden in the build script with a production mode, and this should be removed. But the watch script is set to the development environment. This should disable webpack from compiling production optimizations in concurrency.