Update radon example NB (#3765)

* Initial commit

* Successfully built pymc as dev package with setup.py

* Ran pooled model

* Ran unpooled model

* Finished unpooled section

* Ran first partial pooling model

* Ran second partial pooling model

* Finished varyin intercept model

* Finished varying intercepts and slopes model

* Started group-level predictors section

* Finished group-level predictors section

* Finished correlations among levels section

* Finished prediction section

* Ran whole NB with Arviz dark grid

* Started covariance model section

* Finished covariance model section

* Simplified prediction section with pymc Data container

* Reran whole NB

* Fixed typo

* Integrated Chris comments

* Update ArviZ to remove UserWarning

* Integrate Osvaldo's comments

Author: AlexAndorra