Ensure old config is removed when chaning to/from hourly rotation

When changing an existing rule to hourly, the config should be removed from
/etc/logrotate.d/. Similarly, when changing a rule from hourly, the config
should be removed from /etc/logrotate.d/hourly/.

Fixes #22
Merge pull request #25 from rodjek/issue-22

Ensure old config is removed when chaning to/from hourly rotation