AZ, there is good news and bad news. The bad news is, the Github page instructions appear to be out of date and misleading. The good news is, the current instructions are super-easy. The latest Macchiato release v1.1.3 (Macchiato_Mini_Synthv1_180109.ino) was compiled with Arduino 1.8.4. Try adding MIDI.h and Mozzi to your 1.8.4 libraries as described; then compile the sketch with no further file editing or configuration at all. Flash it to your synth and see if it works.
When my software guy is in tomorrow, I’ll review the Github with him and we’ll update the README with corrected instructions.