Fix make targets for issue #8

Makefile

 .PHONY: dogfood test $(TESTS) clean dist-test dist
 
 dogfood:
-	src/cdiff.py -s
-	git diff | src/cdiff.py
-	git diff | src/cdiff.py -s
+	./cdiff.py -s
+	git diff | ./cdiff.py
+	git diff | ./cdiff.py -s
 
 test: $(TESTS)
 
 $(TESTS):
-	src/cdiff.py tests/$@.diff
-	src/cdiff.py tests/$@.diff -s
-	src/cdiff.py tests/$@.diff | diff -u tests/$@.diff -
-	python3 src/cdiff.py tests/$@.diff
-	python3 src/cdiff.py tests/$@.diff -s
-	python3 src/cdiff.py tests/$@.diff | diff -u tests/$@.diff -
+	python2 ./cdiff.py tests/$@.diff
+	python2 ./cdiff.py tests/$@.diff -s
+	python2 ./cdiff.py tests/$@.diff | diff -u tests/$@.diff -
+	python3 ./cdiff.py tests/$@.diff
+	python3 ./cdiff.py tests/$@.diff -s
+	python3 ./cdiff.py tests/$@.diff | diff -u tests/$@.diff -
 
 clean:
 	rm -f cdiff MANIFEST