Updated the Mifare Classic Value Block example

Updated the `MifareClassicValueBlock.ino` example sketch/program:
* Changed the description, to show that it is an example for the MFRC522 library
* Added link to the GitHub based project for the MFRC522 library
* Expanded the description of the example a little
* Updated the pin layout based on #48 updated README
* Added more comments to explain the process a little better (especially Access Bits stuff)