Expands coverage in test_to_tensor to 1 and 4 image channels (#296)

expands coverage on test_to_tensor to 1 and 4 image channels

test/test_transforms.py

@@ -248,9 +248,11 @@ class Tester(unittest.TestCase):
         assert (y.equal(x))
 
     def test_to_tensor(self):
-        channels = 3
+        test_channels = [1, 3, 4]
         height, width = 4, 4
         trans = transforms.ToTensor()
+
+        for channels in test_channels:
             input_data = torch.ByteTensor(channels, height, width).random_(0, 255).float().div_(255)
             img = transforms.ToPILImage()(input_data)
             output = trans(img)