Script should return 0 on successful completion, even if no campsites are available

[colossatr0n]

Non-zero exit codes should be used to indicate errors that occur during script execution. As long as camping.py completes without exceptions, the script should return a 0. If a user needs to act on whether or not campsites were available, they can do so through grepping the output.

Changing this behavior may break some user scripts, but it will align camping.py with standard scripting practices.

EDIT: Removed portion about cron job behavior. That was just due to output.