Put back "supervised" argument to MethodCost

Print a warning if used.
Change signature of MLP.cost_from_X to be used in MethodCost
Remove deprecated parameter 'supervised' from MethodCost in tutorial
Smaller version of the yaml source in convolution_network.ipynb for test
Skip test if dataset is not there
More information in error message
Fix to TorontoSparsity.get_gradients
Do not require transformer block to have data_specs when space_preserving
Merge pull request #366 from lamblin/fix_conv_tutorial

Fix convolution net tutorial