flask-login for user auth

[ickerio]

Hi team,

Added complete auth system using flask-login. A few features of the PR include

• Login and sign up pages complete (now under auth.html)
• Uses proper password hashing and form validation in line with unit lectures
• Replaced dummy information with proper user info on all pages (i.e initials in avatar on the layout)
• Prevents users from navigating to /login or /signup if the are already authenticated
• Created new logout page accessible from clicking the avatar

Unfortunately ran into a problem with migrations see here and had to completely restart our migrations however I've fixed it and we shouldn't have this issue again.

Another note, as I mentioned in #33 the auth page is looking quite ugly and in need of some form styling like sections, headings and the flashed messages part too.

Please let me know your thoughts, changes etc then I will merge

[HenriScaff]

Looks fantastic well done! Some minor things I noticed while testing:

• after putting all details in on signup page and pressing signup button, it redirects you to /index (good) but it doesn't log you in (minor annoyance) -> requires user to then go login after creating account
• on /leaderboard, the user stats at the top of the page are still the placeholders
• remember me on /login would be nice function to add, but probably out of scope for this PR

Good stuff!