Add ability for users to not have to provide S3 credentials
Add ability for users to not have to provide S3 credentials

This fixes a bug where the app would not start if the user did not provide credentials for S3 for certificate syncing. Closes #116, #118

mitre-cyber-academy/registration-app,mitre-cyber-academy/ctf-scoreboard,mitre-cyber-academy/ctf-scoreboard,mitre-cyber-academy/ctf-scoreboard,mitre-cyber-academy/ctf-scoreboard,mitre-cyber-academy/registration-app,mitre-cyber-academy/registration-app