fix Makefile, fix package.json/scripts

Fix Makefile:
- build minified version of react into `dist/react.min.js`
- build client app into `dist/TodoApp.app.js`

Page uses prebuild client scripts now.

Fix package.json/scripts:
- "postinstall" and "prestart" runs `make dist`
- "start" runs `node TodoAppServer.js`