breaks from adding cocoapod

RN 0.41.2
RNFS 2.1.0 rc 1

there is a problem by using CocoaPods

```
Installing RNFS (2.1.0-rc.1)
Installing React (0.11.0)
```

the react 0.11.0 which messed up other dependencies.
should I still adding cocoapods?

end results:
I get `RNFSFilesTypeRegular` is undefined from the error

I looked at the source code and I found that [this method](https://github.com/johanneslumpe/react-native-fs/blob/master/RNFSManager.m#L515-L528) is private.

```
- (NSDictionary *)constantsToExport
{
return @{
@"RNFSMainBundlePath": [[NSBundle mainBundle] bundlePath],
@"RNFSCachesDirectoryPath": [self getPathForDirectory:NSCachesDirectory],
@"RNFSDocumentDirectoryPath": [self getPathForDirectory:NSDocumentDirectory],
@"RNFSExternalDirectoryPath": [NSNull null],
@"RNFSExternalStorageDirectoryPath": [NSNull null],
@"RNFSTemporaryDirectoryPath": NSTemporaryDirectory(),
@"RNFSLibraryDirectoryPath": [self getPathForDirectory:NSLibraryDirectory],
@"RNFSFileTypeRegular": NSFileTypeRegular,
@"RNFSFileTypeDirectory": NSFileTypeDirectory
};
}
```