Switch to Python unittest

Nose has some inherent problems as it is file-based, so let's switch
to the Python default anyway.

Signed-off-by: martin f. krafft <madduck@madduck.net>
diff --git a/Makefile b/Makefile
index 98ac77b..c3d5aa2 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,7 @@
 PYFILES = $(shell find -name .git -o -name dist -o -name build -prune -o -name '*.py' -print)
 
 tests:
-	python setup.py nosetests
+	python ./run_tests.py
 .PHONY: tests
 
 lint: