compare-puppet-catalogs: fix small bugs

- Fixed the bug that swapped new and old resources missing.
- Fixed the line numbering in diffs.
- Now we output a reminder of the index url when it gets updated.
- Will do a minor version bump

Change-Id: Ie238b78444a4e20751093e2d693d5f534679175d
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>