cnn2d() in models.py is not working

[akpeker]

https://github.com/micah5/pyAudioClassification/blob/54c6c0a0462a8272537092e4c5861c2ba88f5def/pyaudioclassification/models.py#L53 cnn2d function in models.py have layer size issues; gives error by Keras: ValueError: Input 0 is incompatible with layer conv2d_31: expected ndim=4, found ndim=3

Also, there are minor bugs:

• model = Sequential() is missing at the beginning.
• num_classes is used as parameter, but nb_classes is used in the function.