Define get method for received byte size of active task

Author: velitasali

src/main/java/com/genonbeta/CoolSocket/CoolTransfer.java

@@ -581,6 +581,11 @@ public boolean doNotify(CoolTransfer<T> transfer, TransferHandler<T> handler)
 			return true;
 		}
 
+		public long getCurrentTransferredByte()
+		{
+			return mCurrentTransferredByte;
+		}
+
 		public long getLastNotified()
 		{
 			return mLastNotified;