Update to ReactNative 0.49 and react-native-web 1.0 for proper react v16 support

[DaKaZ]

@ericwooley I assume you have seen that version 0.49 of React Native is out along with version 1.0 of react-native-web which are both supporting react v16... I haven't upgraded (yet) but plan to soon. I thought I would open this issue to track progress with the update.

[ericwooley]

@DaKaZ Thanks for the heads up. This is using CRNA so when expo updates they publish it here https://blog.expo.io/

So far they are on 48. as soon as they update, so will I