Add main bundle folder constant #138

src/android/src/main/java/com/RNFetchBlob/RNFetchBlobFS.java

         try {
             p = m.getPackageInfo(s, 0);
             s = p.applicationInfo.dataDir;
-            res.put("DocumentDir", s);
+            res.put("MainBundleDir", s);
         } catch (PackageManager.NameNotFoundException e) {
             e.printStackTrace();
         }

src/ios/RNFetchBlobFS.h

 @property (nonatomic) BOOL appendData;
 
 // get dirs
++ (NSString *) getMainBundleDir;
 + (NSString *) getTempPath;
 + (NSString *) getCacheDir;
 + (NSString *) getDocumentDir;

src/ios/RNFetchBlobFS.m

 
 + (NSString *) getTempPath {
     
-    return [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject] stringByAppendingString:@"/RNFetchBlob_tmp"];
+    return NSTemporaryDirectory();
 }
 
 + (NSString *) getTempPath:(NSString*)taskId withExtension:(NSString *)ext {