* Add backup option
* Only backup shadow file when the OS has one
* Only backup shadow file for SunOS
* Update docs on backup feature
* Add changelog fragment
* Add tests for shadow backup
* Remove backup option, make it automatic
Remove the option to enable/disable backups and make it automatic. Add note to docs describing this behavior.
Change tests to account for new module behavior.
Change section name in changelog fragment since minor_features is not a valid section.
