Add missing IOS7 polyfill interface #119

src/ios/IOS7Polyfill.h

 #ifndef IOS7Polyfill_h
 #define IOS7Polyfill_h
 
+@interface NSString (Contains)
+
+- (BOOL)RNFBContainsString:(NSString*)other;
+
+@end
+
 @implementation NSString (Contains)
 
 - (BOOL)RNFBContainsString:(NSString*)other {