pass batch_size to make_theano_batch

Batch size is needed to test values.

@lamblin [This line](https://github.com/lisa-lab/pylearn2/blob/master/pylearn2/space/__init__.py#L265) is making the assumption that if batch_size == 1 then it should be a row, which is not always the case and causes [This line](https://github.com/lisa-lab/pylearn2/blob/master/pylearn2/monitor.py#L371) to fail.