Add Neil's bit bang SD card code

.gitignore

-*.swp
+*.hex
+*.o
+*.out
 *.swo
+*.swp
 .DS_Store
 build

sd_tests/neil/Makefile

+PROJECT=read_sd
+SOURCES=$(PROJECT).c
+MMCU=attiny84
+F_CPU = 20000000
+
+CFLAGS=-mmcu=$(MMCU) -Wall -Os -DF_CPU=$(F_CPU)
+
+$(PROJECT).hex: $(PROJECT).out
+	avr-objcopy -O ihex $(PROJECT).out $(PROJECT).c.hex;\
+	avr-size --mcu=$(MMCU) --format=avr $(PROJECT).out
+
+$(PROJECT).out: $(SOURCES)
+	avr-gcc $(CFLAGS) -I./ -o $(PROJECT).out $(SOURCES)
+
+program-bsd: $(PROJECT).hex
+	avrdude -p t44 -c bsd -U flash:w:$(PROJECT).c.hex
+
+program-dasa: $(PROJECT).hex
+	avrdude -p t44 -P /dev/ttyUSB0 -c dasa -U flash:w:$(PROJECT).c.hex
+
+program-avrisp2: $(PROJECT).hex
+	avrdude -p t44 -P usb -c avrisp2 -U flash:w:$(PROJECT).c.hex
+
+program-usbtiny: $(PROJECT).hex
+	avrdude -p t84 -P usb -c usbtiny -U flash:w:$(PROJECT).c.hex
+
+program-dragon: $(PROJECT).hex
+	avrdude -p t44 -P usb -c dragon_isp -U flash:w:$(PROJECT).c.hex
+
+program-ice: $(PROJECT).hex
+	avrdude -p t44 -P usb -c atmelice_isp -U flash:w:$(PROJECT).c.hex