fixed classification prediction for multiple nodules
fixed classification prediction for multiple nodules

Bug fixed. When the length of the nodules list is more then 1 – prediction fails as follows:

```
~/concept-to-clinic/prediction/src/algorithms/classify/src/gtr123_model.py in predict(ct_path, nodule_list, model_path)
    275     results = []
    276 
--> 277     for nodule, (cropped_image, coords) in zip(nodule_list, patches):
    278         cropped_image = Variable(torch.from_numpy(cropped_image[np.newaxis, np.newaxis]).float())
    279         cropped_image.volatile = True

ValueError: too many values to unpack (expected 2)
```

More details [here](https://github.com/concept-to-clinic/concept-to-clinic/pull/272#issuecomment-355413434).

## CLA
- [x] I have signed the CLA; if other committers are in the commit history, they have signed the CLA as well
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