The Sha204Personalizer has been converted to a SecurityPersonalizer. It takes care of generation and storage of keys and data to both ATSHA204A and nonvolatile storage (EEPROM). Library has been updated to read any software security related data from the corresponding EEPROM locations. The effect this has is that any node using any security feature has to execute the personalizer at least once to store appropriate values. The benefit of this is that the software no longer contain sensitive data such as HMAC or AES keys. Whitelists still are stored in software as they are variable in size.
For information on installing libraries, see: http://arduino.cc/en/Guide/Libraries