TODO

1. Add the ability to specify an alternate configuration as an argument, which
   may be useful for once-off backups.
2. Include more comprehensive documentation.
3. Add S3 backup support.
4. The ping test should only be ran once per host, not once per entry.
5. The ping test should have a point. Ping test failure should prevent an
   rsync attempt.
6. Once 5 is implemented, the ping test should optionally be disabled for any
   given host. This should be set in the configuration file, or globally
   via a command line argument.
7. Keep track of file "meta-data" such as ownership and
   permissions. When hard-linking, permission changes are not
   preserved. This could even be considered a bug, but I currently
   consider it a known limitation.