Enable user sign up

[Armitage35]

Current behavior
Since Issue #41 we now know if a user has already used this browser to access Day2Day. We now need to enable him to access his / her task on any device and browser he / she wants to use.

Expected behavior

• Verify if the user's already logged in
• Make a sign up page (reuse from https://codepen.io/alexdevero/pen/vNRqLL)
• If not display the sign up page
• Send the form info to the server
• On the server check that the information submitted are OK (required fields + format)
• Save those infos in mongo
• Redirect user to Day2Day app page
• Grant access to the user and set his cookie to his user id
• If the info are not valid, send a warning to the client (req.flash??)
• Display potential registration errors in the UI
• Check that this email is not already taken by another user
• If user has cookie and accesses /auth.html send him over to tasks
• Make sign up page responsive using bootstrap
• Add a cool registration successful animation
• nice to have: hash the password so as not to save it in clear text (https://www.abeautifulsite.net/hashing-passwords-with-nodejs-and-bcrypt)

[Armitage35]

Careful not to forget what our user schema looks like.