Changes on ADVI functions (#1499)

* pep8

* Change the definition of optimizers

* Use theano float type

* ENH Support models without global RVs

* Fix ADVI code for tests

* Update notebooks that use ADVI

* Add a convolutional vae notebook as an example

Author: taku-y

docs/source/examples.rst

@@ -54,5 +54,5 @@ ADVI
    notebooks/GLM-hierarchical-advi-minibatch.ipynb
    notebooks/lda-advi-aevb.ipynb
    notebooks/bayesian_neural_network_advi.ipynb
-
+   notebooks/convolutional_vae_keras_advi.ipynb