fixed typo (pytorch#182)

changed `confortable` to `comfortable`

Author: Max Mikhaylov

advanced_source/neural_style_tutorial.py

@@ -103,7 +103,7 @@
 we need: indeed, with PyTorch, all the gradients are automatically and
 dynamically computed for you (while you use functions from the library).
 This is why the implementation of this algorithm becomes very
-confortable with PyTorch.
+comfortable with PyTorch.
 
 PyTorch implementation
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