Fix cuda (#31)

* Fix cuda

* Update pytorch.py

One more gpu->cpu

* fixed pep8 violations and test coverage

foolbox/models/pytorch.py

@@ -49,6 +49,8 @@ def batch_predictions(self, images):
         images = Variable(images, volatile=True)
         predictions = self._model(images)
         predictions = predictions.data
+        if self.cuda:  # pragma: no cover
+            predictions = predictions.cpu()
         predictions = predictions.numpy()
         assert predictions.ndim == 2
         assert predictions.shape == (n, self.num_classes())
@@ -82,12 +84,17 @@ def predictions_and_gradient(self, image, label):
         grad = images.grad
 
         predictions = predictions.data
+        if self.cuda:  # pragma: no cover
+            predictions = predictions.cpu()
+
         predictions = predictions.numpy()
         predictions = np.squeeze(predictions, axis=0)
         assert predictions.ndim == 1
         assert predictions.shape == (self.num_classes(),)
 
         grad = grad.data
+        if self.cuda:  # pragma: no cover
+            grad = grad.cpu()
         grad = grad.numpy()
         grad = np.squeeze(grad, axis=0)
         assert grad.shape == image.shape