Fix test and update gitignore

.gitignore

@@ -1,3 +1,4 @@
+*.nd2
 run.py
 # Byte-compiled / optimized / DLL files
 __pycache__/

tests/test_reader.py

@@ -40,4 +40,4 @@ class TestReader(unittest.TestCase):
         with ArtificialND2('test_data/test_nd2_reader.nd2') as _:
             with ND2Reader('test_data/test_nd2_reader.nd2') as reader:
                 timesteps = reader.timesteps
-                self.assertEquals(timesteps, None)
+                self.assertEquals(len(timesteps), 0)