Difference between Arduino IDE giving me headaches
To get RF24 working:


Download the latest IDE (not 1.0*)
Use the library manager to download the
latest RF24.
See https://github.com/TMRh20/RF24/issues/236#issuecomment-205354077
about what core to use.  
Don't forget to define ATTiny in the sketch
Ex: #define __AVR_ATtiny84__
(84, 44, 24 are the choices)


ATTiny* do not have SPI, that's why it can't find SPI.h (SPI library).