Add an article about adding Firefox Account integration for Daybed.

Could you please have a look and some feedbacks about this article. @leplatrem @ametaireau @tarekziade 
But on the other hand, when a user wants to user the same token on all her devices, he needs a way to share it easily and securely.

There are several ways to do it, among them:
* Put the token in the URLs of your applications (like 0bin, doodle, google docs, ...), and share the URLs on your devices using synced bookmarks for example
* Build the token from the authorization header
* Build the token from a user id obtained via OAuth