ValueError: could not broadcast input array from shape (96,96,4) into shape (96,96)

I'm having the similar trouble as in #26. Not sure if I'm doing something wrong or if there's a fix. I'm using my own image dataset all scaled to 96x96. Stack trace below.

Image:
`PNG 96x96 96x96+0+0 8-bit sRGB 7.2KB 0.000u 0:00.000`

```
Traceback (most recent call last):
File "main.py", line 99, in
tf.app.run()
File "/home/ubuntu/.local/lib/python2.7/site-packages/tensorflow/python/platform/app.py", line 44, in run
_sys.exit(main(_sys.argv[:1] + flags_passthrough))
File "main.py", line 82, in main
dcgan.train(FLAGS)
File "/home/ubuntu/GANs/model.py", line 186, in train
sample_inputs = np.array(sample).astype(np.float32)
```