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?
The indenting here is incorrect (also, see PEP8). Hanging indents should only increase 1 level, so it should be
```
x.tag.test_value = np.random.random(
    get_debug_values(X)[0].shape)
```