Check y

By using the get_debug_values() function and with flag "theano.config.compute_test_value" turned on, we can now check the value of Y before computing kl or elemwise_kl. Note that this feature should only be expected to work in test time, not for passed values in a real function call.

Should we check every mode of "theano.config.compute_test_value" in the unit test? Or, since it is only a unit test for kl (or elemwise_kl), just testing it on one of the mode will be OK?
This check doesn't seem right. If `Y = [0.1, 0.9]` this evaluates to true, while it shouldn't. There must be a dozen ways to test this, but one would be to check if:

```python
np.sum(Yv == 0) + np.sum(Yv == 1) == Yv.size
```