implemented adagrad (haven't tested it yet though...)
converted all 'cost' parameters to 'loss'. made other cosmetic changes and also added adagrad - seems to work, but haven't checked for correctness
fixed up the autoencoder, should now be usable for creating deep networks. next task - write a tied-weights autoencoder
started incorporating tied-weights into the autoencoder. need to still write the code for setting the weights and doing forward propagation specific to this case, in the autoencoder class