Syncers and before_hook and after_hook added. Example recipes added

I changed the default backup path for cron to backup without the path, as the ruby bin_dir does not contain the 'backup' program on the Gentoo OS. Able to resolve with cron_path

before_hook and after_hook executed ruby code from the input string.

Examples usage for backup_generate_model
```
before_hook <<-heredoc
    unless system("/opt/backup/before_backup_check.sh")
        raise "There was an error"
    end
heredoc

```