adding simple countdown to the challenges page
updated styles and added image for bg for new counter system
Adding a validator to challenges

We also don't want to show the countdown if the challenge is expired so this commit addresses that as well.
removing old files
created_at would be nil so it should be set to Time.now first
Anonymize users until challenge is finished
Fix the other places display_user was used
Merge pull request #17 from libryder/anon_sol

Anonymize users until challenge is finished
Merge pull request #15 from libryder/countdown

Countdown