pwnyaa: cache challs of ksnctf
pwnyaa: cache challs of ksnctf

- ksnctf doesn't have user-profile page, and the score of the
challs are not shown in log-page. Therefore, chache data of challs
in the module and reuse it for better appearance of user profiles.
The cache is updated every 12 hours.

tsg-ut/slackbot,tsg-ut/slackbot,tsg-ut/slackbot,tsg-ut/slackbot,tsg-ut/slackbot,tsg-ut/slackbot