Shuffle binary packages:
 * Renamed gunicorn-common to gunicorn-examples.  This now only contains the
   examples (i.e. not the initscript).
 * gunicorn-examples is Suggests.

debian/gunicorn-debian should *not* use /usr/bin/env.  Since it's a system
script, it must use /usr/bin/python.  It gets installed into /usr/sbin in the
gunicorn binary package.

Copy debian/gunicorn-debian to gunicorn3-debian and port it to Python 3.  It's
a /usr/bin/python3 shebang.  It gets installed into /usr/sbin in the gunicorn3
binary package.