fixes the issue #490 such that SparseDataset works with the new style of the iterator with data_specs
adding a test unit for issue #490 in addition to completing the SparseDataset class
removing a comment
correcting comment #490
updating issue #490
updating the issue #490 to add module_level docstring
updating ticket #490 to cover the comments of Xavier.
updating issue #490 to apply comments of Xavier
applying modification for ticket #490 to use Train object.
changing a comment for issues #490
adding comments to the dummy classes in test_sparse_dataset (ticket #490)
Updating the test_sparse_dataset for ticket #490 to update module_level and
class level comments
fix maxout mnist
fix cifar10, svhn
updating the DummyCost Class for ticket  #490
Merge pull request #840 from memimo/maxoutmnist

Maxoutmnist
Adding comment to issue #490
adding a line issue #490
Refactoring + some fixes.
Removed unnecessary code and fixed the doc.