A GNOME interface for reading the Diamond Comics Previews catalog.

Enhancements
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- Fixed a bug where all files where loaded twice when opening a Previews catalog.
- Changed the look of the item descriptions.
- New series are in italics in the item list.
- Added a view where only the new series are shown.
- Added a commandline tool called previews-downloader.py that takes a year and a month, and then goes out and downloads all the needed Previews files.
- Now displays the number of items currently shown in the status bar.
- Added an option to toggle the display of "Offered Again" items (O/A).