code: public String chunkedUploadFirst(byte[] data, int dataOffset, int dataLength)
          throws DbxException
      {
          return chunkedUploadFirst(dataLength, new DbxStreamWriter.ByteArrayCopier(data, dataOffset, dataLength));
      }
docs: Upload the first chunk of a multi-chunk upload.
  
  @param data
  The data to append.
  @param dataOffset
  The start offset in {@code data} to read from.
  @param dataLength
  The number of bytes to read from {@code data}, starting from {@code dataOffset}.
  
  @return
  The ID designated by the Dropbox server to identify the chunked upload.