Integrated react-router

For #1 . Feel free to ask any questions. Decided against `react-router-bootstrap` in the end because it was never really finished, won't ever be and we can do without. `react-router` has a flexible and well-documented API:  https://github.com/rackt/react-router/tree/master/docs/api
This is not necessary and dangerous. the middleware  app.use(express.static(path.join(__dirname, 'public'))); already takes care of public files, plus with this implementation the only file we can get is index.html therefore making it impossible to get any images or any other static content not packed by webpack