contrib: add a PyQt4 example

Add an example demonstrating how to use a custom handler
to serialize PyQt4.QtCore.QPointF instances.
requirements-3.txt: add simplejson and feedparser

Signed-off-by: David Aguilar <davvid@gmail.com>
handlers: add support for python3.2

Detect the varying results returned from the json library and
normalize them so that we can consistently call b64decode().
This makes us python3.2-compatible, sans simplejson.

Closes #51
Signed-off-by: David Aguilar <davvid@gmail.com>
tests: fix tests for python3.2

Python 3.2 does not support unicode literals so the simplejson
module is not available there.

Skip the simplejson tests when on Python 3.2 and hide the
backend tests that are not available under Python 3.x so that
`nosetests --with-doctest` does not see them.

Closes #51
Signed-off-by: David Aguilar <davvid@gmail.com>