Fixed issue with installing gflags
diff --git a/Makefile b/Makefile
index 4ae3f1d..1fc70e6 100644
--- a/Makefile
+++ b/Makefile
@@ -11,9 +11,9 @@
 
 .PHONY: prerelease
 prerelease:
-	python2.4 runtests.py --exit_on_failure
-	python2.6 runtests.py --exit_on_failure
-	python2.7 runtests.py --exit_on_failure
+	python2.4 runtests.py tests --exit_on_failure
+	python2.6 runtests.py tests --exit_on_failure
+	python2.7 runtests.py tests --exit_on_failure
 	-rm dist/*
 	python setup.py clean
 	python setup.py sdist