I thought that was nice until someone showed me NicoHood's IRLremote
So with some minor changes for Attiny it's quite a decent size with a lot more desirable features & less fiddling to Transmit/Receive.
Receive_PinInterrupt.ino
Removed
#define pinIR 2
& References to Serial.
Changed
attachInterrupt(digitalPinToInterrupt(pinIR), IRLinterrupt<IR_ALL>, CHANGE);
To
attachInterrupt(0, IRLinterrupt<IR_ALL>, CHANGE);
Send_Button.ino
No change need 
A very nice library for any AVR