Now that the application is going to have multiple pages, vote data makes no sense
to keep with the user.
The user struct will be used everywhere to check for authentication, which is not
the case for previous votes.
Create a new struct and function in src/vote.rs to retrieve existing votes and
use them in places where user.votes was used previously.
Remove vote-related code from src/auth.rs and the week number dependence that it
required.
