Improve Travis build speed by storing build cache
Improve Travis build speed by storing build cache

jotomo/AndroidAPS,Heiner1/AndroidAPS,MilosKozak/AndroidAPS,jotomo/AndroidAPS,Heiner1/AndroidAPS,PoweRGbg/AndroidAPS,Heiner1/AndroidAPS,Heiner1/AndroidAPS,MilosKozak/AndroidAPS,winni67/AndroidAPS,jotomo/AndroidAPS,MilosKozak/AndroidAPS,winni67/AndroidAPS,PoweRGbg/AndroidAPS,PoweRGbg/AndroidAPS