Add a configuration file.

We have two targets for the configuration file:

- dev for local deployment, where this uses localhost:8000,
- prod where it uses daybed.io behind TLS.

To do so, we are including a new config.js file in the HTML and attaching
document.formbuilder with some configuration information.
Put the form editor in a separate react component.

Also update to fluxxor 1.5 which provides a new FluxMixin.
Add a way to list the forms.

Here, we introduce a router to our react application.
We discovered along the way that the react-bootstrap weren't directly
compatible with react-router and had to use a specifc implementation of them
(and lost a couple hours in the meantime).

As the session was shared with a token in the hash part of the url, it was
coliding with how routing is done by react-router, so we're storing the daybed
session in localStorage for now (but this will probably evolve in the future).