TODO

- add 'silent'
- handle errors from mysqldump
- check that gpg is installed
- support percona XtraBackup as an option instead of mysqldump [patches anyone :) ?]
- backup validation:
  - support for 'minsize' opition in backup that will check that produced backup is at least the expected size
    this should catch many backup failure scenarious (like broken mysql connection, insufficient disk space etc.
- support differencial backups
  - it should be fairly easy for filesystem backups using tar's built in incremental functionality.
  - for mysql need to use XtraBackup
  - or we can keep the previous dump locally and store only diff with the latest dump