absolute value

[micuat]

Hi, I found the gyro reading in iOS is velocity and not absolute value (I haven't tested on Android so I don't know if it's the same). I did a quick hack to read absolute orientation instead of velocity:
https://gist.github.com/micuat/8382a28f6cc32a4fb2862544c56fb784#file-cdvgyroscope-m-L53

I guess ideally the API can switch between velocity and absolute orientation. Is this something I should make a PR? Otherwise I will create my own plugin...