Try PySide then PyQt4 for Qt4 examples.
Use the correct connect method for PySide.

This should make the examples work with both PyQt4 and PySide (I can only test the later)
Use the same logic as MPL uses when picking Qt interface.

Thanks to Michael Droettboom (https://github.com/matplotlib/matplotlib/pull/2221#issuecomment-21108901)
Merge pull request #2221 from DanielO/master

Try PySide then PyQt4 for Qt4 examples.