cleanup more files after test_simple

tests/test_simple.py

@@ -14,6 +14,7 b' def clean_dir():'
     map(os.remove, glob.glob("./tests/*.rst"))
     map(os.remove, glob.glob("./tests/*.png"))
     map(os.remove, glob.glob("./tests/*.html"))
+    map(os.remove, glob.glob("./tests/test_files/*"))
 
 
 @nt.with_setup(clean_dir, clean_dir)