fix non compliant Python3 print statement

spi.py print statement won't work in Python 3, so just a small fix
tested using
python3 setup.py install
and
python setup.py install

output is:
pi@raspberrypi ~/libbcm2836-py3 $ sudo python3 setup.py install
running install
running build
running build_py
creating build
creating build/lib
creating build/lib/libbcm2835
copying ./libbcm2835/__init__.py -> build/lib/libbcm2835
copying ./libbcm2835/_bcm2835.py -> build/lib/libbcm2835
copying ./libbcm2835/spi.py -> build/lib/libbcm2835
running install_lib
copying build/lib/libbcm2835/__init__.py -> /usr/local/lib/python3.2/dist-packages/libbcm2835
copying build/lib/libbcm2835/_bcm2835.py -> /usr/local/lib/python3.2/dist-packages/libbcm2835
copying build/lib/libbcm2835/spi.py -> /usr/local/lib/python3.2/dist-packages/libbcm2835
byte-compiling /usr/local/lib/python3.2/dist-packages/libbcm2835/__init__.py to __init__.cpython-32.pyc
byte-compiling /usr/local/lib/python3.2/dist-packages/libbcm2835/_bcm2835.py to _bcm2835.cpython-32.pyc
byte-compiling /usr/local/lib/python3.2/dist-packages/libbcm2835/spi.py to spi.cpython-32.pyc
running install_egg_info
Removing /usr/local/lib/python3.2/dist-packages/libbcm2835-1.0.egg-info
Writing /usr/local/lib/python3.2/dist-packages/libbcm2835-1.0.egg-info

pi@raspberrypi ~/libbcm2836-py3 $ sudo python setup.py install
running install
running build
running build_py
creating build/lib.linux-armv6l-2.7
creating build/lib.linux-armv6l-2.7/libbcm2835
copying ./libbcm2835/__init__.py -> build/lib.linux-armv6l-2.7/libbcm2835
copying ./libbcm2835/_bcm2835.py -> build/lib.linux-armv6l-2.7/libbcm2835
copying ./libbcm2835/spi.py -> build/lib.linux-armv6l-2.7/libbcm2835
running install_lib
creating /usr/local/lib/python2.7/dist-packages/libbcm2835
copying build/lib.linux-armv6l-2.7/libbcm2835/__init__.py -> /usr/local/lib/python2.7/dist-packages/libbcm2835
copying build/lib.linux-armv6l-2.7/libbcm2835/_bcm2835.py -> /usr/local/lib/python2.7/dist-packages/libbcm2835
copying build/lib.linux-armv6l-2.7/libbcm2835/spi.py -> /usr/local/lib/python2.7/dist-packages/libbcm2835
byte-compiling /usr/local/lib/python2.7/dist-packages/libbcm2835/__init__.py to __init__.pyc
byte-compiling /usr/local/lib/python2.7/dist-packages/libbcm2835/_bcm2835.py to _bcm2835.pyc
byte-compiling /usr/local/lib/python2.7/dist-packages/libbcm2835/spi.py to spi.pyc
running install_egg_info
Writing /usr/local/lib/python2.7/dist-packages/libbcm2835-1.0.egg-info