Backup container for mongo instances

This image provides a cron daemon that runs daily backups from mongo (clustered or single instance) to Amazon S3.

Following ENV variables must be specified:

• MONGO_URL contains the connection string for mongodump command line client (option -h)
• MONGO_USER contains the username
• MONGO_PASSWORD password of a user who has access to all dbs
• S3_URL contains address in S3 where to store backups
• bucket-name/directory
• S3_ACCESS_KEY
• S3_SECRET_KEY
• CRON_SCHEDULE cron schedule string, default '0 2 * * *'