Update densenet.py (#368)

* Update densenet.py

added missing weight init for densenet

* Update densenet.py

following official implementation [here](https://github.com/liuzhuang13/DenseNet/blob/master/models/densenet.lua#L160)

* Update densenet.py

changed to nn.init & fixed lint

torchvision/models/densenet.py

@@ -153,6 +153,16 @@ class DenseNet(nn.Module):
         # Linear layer
         self.classifier = nn.Linear(num_features, num_classes)
 
+        # Official init from torch repo.
+        for m in self.modules():
+            if isinstance(m, nn.Conv2d):
+                nn.init.kaiming_normal(m.weight.data)
+            elif isinstance(m, nn.BatchNorm2d):
+                m.weight.data.fill_(1)
+                m.bias.data.zero_()
+            elif isinstance(m, nn.Linear):
+                m.bias.data.zero_()
+
     def forward(self, x):
         features = self.features(x)
         out = F.relu(features, inplace=True)