Support for React Native v0.40

[oureta]

On RN v0.40, iOS native headers have been moved. Imports of RN Headers should be changed from:

#import "RCTBridgeModule.h"

to

#import <React/RCTBridgeModule.h>

[justinobney]

https://medium.com/@thisismissem/how-to-upgrade-react-native-modules-in-a-backwards-compatible-manner-a5b5c48d590c#.p714l4p8r