Got rid of notebook visualization errors for IPython 3.

[moorepants]

@jcrist Here is a start to fixing issue #142.

• There are no merge conflicts.
• If there is a related issue, a reference to that issue is in the
  commit message.
• Unit tests have been added for the bug. (Please reference the issue #
  in the unit test.)
• The tests pass both locally (run nosetests) and on Travis CI.
• The code follows PEP8 guidelines. (use a linter, e.g.
  pylint, to check your code)
• The new feature is documented in the Release
  Notes.
• The code is backwards compatible. (All public methods/classes must
  follow deprecation cycles.)
• All reviewer comments have been addressed.

[moorepants]

Closing this.