MatplotlibViewer still has problems in IPython notebook

[guyer]

Some improvements were made in #368, but MatplotlibViewers still don't render well in the IPython notebook.

IPython 3.2.0-8b0eef4 raises TypeError: show() got an unexpected keyword argument 'block'. This is potentially a bug in IPython, as pylab.show documents:

A single experimental keyword argument, block, may be
set to True or False to override the blocking behavior
described above.

Filed ipython/ipython#8705, nonetheless, it's our problem now.

[guyer]

Beyond this, it's clumsy to have to clear_output() and display(), but only when in the notebook. plot() should just work.