I just got this to work last night. In the Base64 library open the Base64.cpp. Change the <avr/pgmspace.h> to "pgmspace.h" save and close. copy pgmspace.h into folder called pgmspace in your normal arduino libraries folder. If open close and reopen Arduino IDE. It compiles fine.
I also had to connect my GPIO0 like i was flashing firmware. All worked out great.