All Outputs of Network are the Same (Python API)

Hi, I receive the same output for every input image I give the Overfeat model using the Python API. Minimal code to reproduce:

```
>>> overfeat.init(path_to_weights, 0)
>>> img = np.random.rand(3, 231, 231).astype(np.float32)
>>> r1 = overfeat.fprop(img)
>>> img = np.random.rand(3, 231, 231).astype(np.float32)
>>> r2 = overfeat.fprop(img)
>>> all(r1 == r2)
True
```