Added option to make_spectrogram to make either a pickled dataset or actual spectrograms. The dataset incorporates a flattened array of the spectrogram and the classification string. Cast the data to int8 - the spectrograms look just the same and it's a huge size savings. Fixed memory leak by closing the pyplot figures each time. Note that there's probably a better way to distinguish between mp3 and wav files - the output of the 'file' command varies from system to system...
Modified make_dataset to create the spectrograms as bare data and save these as a pickled object for use by the Theano modules.