CyanogenMod emulation
The Contacts app doesn't require any specialized device features, so you should be able to test your modifications in an AVD created from the images you download via Studio's SDK Manager. These are just basic Android images, not Cyanogen, but if you're not tying into some special feature of Cyanogen or i9100 hardware, then it will be adequate.

Once you get things working in an emulator, connect the i9100 to your development box and test the app for real. You'll need to enable the Developer Options menu and turn USB debugging on before Studio will see that i9100 as a run configuration target.