code: public Msg putShortString(String data)
      {
          if (data == null) {
              return this;
          }
          ByteBuffer dup = buf.duplicate();
          dup.position(writeIndex);
          writeIndex += Wire.putShortString(dup, data);
          return this;
      }
docs: Puts a string into the message, prefixed with its length.
  Users shall size the message by adding 1 to the length of the string:
  It needs to be able to accommodate (data.length+1) more bytes.
  
  @param data a string shorter than 256 characters. If null, defaults to a no-op.
  @return the same message.