message: Updated README to refelect Code 39 support
diff: | 1D product | 1D industrial | 2D
  | ------------------ | -------------------- | --------------
  -| ~UPC-A~ | ~Code 39~ | QR Code
  +| ~UPC-A~ | Code 39 (_no docs_) | QR Code
  | ~UPC-E~ | ~Code 93~ | Data Matrix (_no docs_)
  | ~EAN-8~ | Code 128 (_no docs_) | ~Aztec (beta)~
  | EAN-13 (_no docs_) | ~Codabar~ | PDF 417 (_in-progress_)
  