BackAndroid is deprecated

[JoaoBGusmao]

Following this stack, we can note that src/utils/index.js is importing BackAndroid as DeprecatedBackAndroid, and that's what causes the error.

 Test suite failed to run

    Invariant Violation: BackAndroid is deprecated and has been removed from this package. Use BackHandler instead

      at invariant (node_modules/invariant/invariant.js:40:15)
      at Object.invariant [as BackAndroid] (node_modules/react-native/Libraries/react-native/react-native-implementation.js:373:5)
      at Object.DeprecatedBackAndroid (node_modules/react-native-material-ui/src/utils/index.js:9:36)
      at Object.<anonymous> (node_modules/react-native-material-ui/src/RippleFeedback/RippleFeedbackIOS.react.js:13:1)

[JoaoBGusmao]

I can see it was fixed already, but it doesn't seem to have been published to npm https://github.com/xotahal/react-native-material-ui/blob/master/src/utils/index.js