It was unintentional that the latest app update would support iOS 6. It's a very old OS, and the new app is taking advantage of a newer OS features.
We've looked at the issue and don't believe there's any way we can support iOS 6 moving forward. The app should not have been downloadable on iOS 6 and that will be fixed in our next update.
That said: this problem was only on the paid version. If you download the "Lite" version of the Cyanide and Happiness app to your iOS 6 device, it *should* prompt you to download the much older version of the app, which should work correctly on iOS 6.
Side note: It's time to consider updating to iOS 7 or later! See: http://david-smith.org/iosversionstats/