I had a similar issue with nearly ALL of my apps that required an update when I updated to iOS 8. This is an App Store problem since the apps themselves are not involved in the update process at all. Here are the things I did did to get my updates unstuck:
- Make sure I'm connected to a good wifi network
- Power on and off the device (reboot it)
- Tap on the app (mine said "waiting") to see if that restarts the download. I've seen this work in the past, but it didn't work for me this time.
- Go to the App Store app. Go to the updates tab. If there are any updates available, update those.
- Repeat 4. I found that as I did this, the updater would get unstuck and the update for each of my apps eventually restarted. I may also have used the "Purchased" section to download or update apps as well.
Please let me know if any of this works, or if you find another way and I'll add that to this list.