Fixes for firmware/SDK 2.5

Hullo!

Your app is currently broken on firmware 2.5, due to a change made to snprintf that dropped support for C99 formatters like `%hhu`. The app also won't compile against SDK 2.5, due to relying on private symbols that moved around. This pull request change `%hhu`

- %hhu is broken in firmware 2.5, even for apps build against old firmware
- The private PebbleAppInfo was renamed to PebbleProcessInfo in SDK 2.5

Note that I don't actually have a Starbucks card, so I can't test this properly.