Problem building for Python 3

[PanderMusubi]

I had a problem building for Python3. I think the README should state

$ python3 setup.3.py build
$ python3 setup.3.py install

instead of

$ python setup.3.py build
$ python setup.3.py install

However pip3 install aspell-python-py3 also does the trick. That may be added to README as well.

PS Vote for https://bugs.launchpad.net/ubuntu/+bug/1474451 to get this library packaged for Ubuntu