Avoid pylab and use the specific imports instead.

The pylab "interface" import a lot of things (too many)... and there is a lot of people (including me) trying to avoid the spread of its use. You can check a blog post about the problem of importing pylab here: http://carreau.github.io/posts/10-No-PyLab-Thanks.ipynb.html

Also, using the specific imports makes easy to integrate the matplotlib examples in bokeh mpl examples, which I will need to do to test the LineCollection support.