remove unnecessary if
add option to preserve file mod times
Merge branch 'YetAnotherNerd'

Thanks to YetAnotherNerd, we are now able to preserve file mtime when
doing non-destructive operations (metaflac vs flac).

Thanks!
Documentation added and bumped the config revision

Helped explain the various values accepted for the new
'preserve_modtime' option, and incremented the script and configuration
revision version to allow users to be aware of the new changes.