Update RF12_Demo_atmega328.ino

Increase transmit buffer sizes from 20 to 66 bytes for use by Emoncms PacketGen Modules
Merge pull request #8 from Bra1nK/patch-1

Update RF12_Demo_atmega328.ino Increase transmit buffer sizes from 20 to 66 bytes for use by Emoncms PacketGen Modules
create hex file with new packet size increase
fix pre-compiled hex file using V11 JeeLib