Fix build issue with some BUCK/clang environments

[fmoo]

Some build environments need to use #import <...> to pull in the react bridge. Other projects such as react-native-orientation do this: https://github.com/yamill/react-native-orientation/blob/master/iOS/RCTOrientation/Orientation.h#L7-L11

[fulvio-m]

This fix is necessary for us, RN 0.55.2.