Added size information for inception v3 (#719)

* Added size information for inception v3

Since inception v3 expects in contrast to the other models a size
of 299x299x3 I added a small note in the docstring to point that out
(addresses #560)

* inception size info in note box; fixed line length

* removed trailing whitespace

torchvision/models/inception.py

@@ -17,6 +17,10 @@ def inception_v3(pretrained=False, **kwargs):
     r"""Inception v3 model architecture from
     `"Rethinking the Inception Architecture for Computer Vision" <http://arxiv.org/abs/1512.00567>`_.
 
+    .. note::
+        **Important**: In contrast to the other models the inception_v3 expects tensors with a size of
+        299x299x3, so ensure your images are sized accordingly.
+
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet
     """