Fix contest scoreboard to properly color AC submissions green (#31)

[SuperCl4sh]

Fixes #31.

[SuperCl4sh]

Looking at each of the contest formats, there appears to be the exact same display_user_problems functions in them. Perhaps it might be worth removing them, then simply importing them from default.py. Alternatively, since the the default contest is passed as a constructor for each of the contest formats, super() could be used. This would reduce code redundancy while optimizing future code updates to this function.

[zecookiez]

Can you send a screenshot from your testing? This looks okay but I don't know if there are any existing scoreboards on the platform that have this issue.

[SuperCl4sh]

This is before the changes:

This is after the changes:

An example on the site can be found here.