add some tests

@mattpap I am using BeautifulSoup to inspect our embedding HTML closely. What is the easiest way to add it to our test install, everything is conda now correct? We will need to make a conda package and put it somewhere. 

@mattpap, @damianavila, @kdodia, @tabchas, @hhuuggoo, @JosephCottam  (also ping @pzwang) 

All, we have been fairly lax in keeping up tests for Bokeh, As more people start using Bokeh and we want to move pieces forward this is going to become a liability for us. I'd like to use this PR to collect a reasonable chunk of new tests. In particular, I would like **everyone** to contribute **something** to this PR. It does not have to be something huge or complicated, just something to get back some practice of test writing.