Fixed some errors in example code of readme file.

[AlbertoCasasOrtiz]

Hello,

I'm using your QR code generator and I notice there were some errors in the example code of the readme. The list below includes the changes I have made.

• The line next line didn't had the version number:
  uint8_t qrcodeBytes[qrcode_getBufferSize(3)];
• The tipes of the variables in the for loops appeared as uint8 instead of uint8_t, producing a compilation error.
• There was a missed parenthesis in the if inside the for loops, producing a compilation error.
  if (qrcode_getModule(&qrcode, x, y))

I hope this corrections helps people to use this great code you have created.

Best regards.
Alberto Casas Ortiz.