Implement support for basic CSS modules

Also includes:

• Switch everything to camelCase
• Switch to using webpack to build browser script (woohoo!)
• Update node target for babel-preset-env to latest lts version
• Remove postbuild.js in favor of dist/cli/index.js so cli will still work with dev build
• Switch to using include everywhere we're using indexOf
• Use import for everything in the CLI
• Move gaze logic to a separate fileWatcher.js
• Update various other packages and add package-lock.json
• Switch to using webpack module key (it's unique!) instead of an md5 hash for targeting correct markup to replace. We were using node crypto for the hash, which was adding a whole crapload of modules to the browser build.
• Switch to using the more standard index.js for both web and cli entry points
• Remove prebuild script (which used eslint cli) in favor of eslint-loader now that we're using webpack for browser build also