message: updated pdf417 readme status
diff: | ~~UPC-A~~ | Code 39 | QR Code |
  | ~~UPC-E~~ | ~~Code 93~~ | Data Matrix |
  | EAN-8 | Code 128 | ~~Aztec~~ \* |
  -| EAN-13 | ~~Codabar~~ | ~~PDF 417~~ \* |
  +| EAN-13 | ~~Codabar~~ | PDF 417 |
  | | ITF | ~~MaxiCode~~ |
  | | RSS-14 |
  | | ~~RSS-Expanded~~ \* |
  