Fix badge, add missing test makefile

tests/Makefile

@@ -0,0 +1,18 @@
+%.o: %.c
+	gcc -I../src -ansi -Wall -Werror -c -o $@ $<
+	for file in $$(cat $$(echo $@ | sed 's/\.o$$//').deps); do \
+		gcc -I../src -ansi -Wall -Werror -c -o ./$${file}.o ../src/$$file.c ; \
+	done
+
+%.elf: %.o
+	gcc -o $@ $^ $$(cat $$(echo $@ | sed 's/\.elf$$//').deps | sed 's/$$/\.o/g')
+
+
+all_targets:=$(shell ls *c | sed 's/\.c$$/\.elf/g')
+
+all: $(all_targets)
+
+.PHONY: clean
+clean:
+	rm -f *o
+	rm -f *elf