Adding versions to Gemfile

Prevent future problems with versions
Update rails version

Include latest security fixes
Do not use the same secret token on production

Read secret token from the environment variables.

$ export SECRET_TOKEN=my-secret-token
Merge pull request #7 from nhocki/master

Some rails security fixes
Update README.md
Update README.md
Update README.md

.md format
Update README.md
Update README.md
Deleting judge2 folder
Merge branch 'dev' of github.com:sebasutp/utpjudge into dev