Editor’s note: The following review is part of Macworld’s GemFest 2013. Every day (except Sunday) from mid-July until late September, the Macworld staff will use the Mac Gems blog to briefly cover a standout free or low-cost program. You can view a list of this year’s apps, updated daily, on our handy GemFest page, and you can visit the Mac Gems homepage to see past Mac Gems reviews....