setup.py: fix up classifiers
setup.py: fix up classifiers

We,

1. don't support python 2.7 any more
2. are probably stable/production now, since we've been using this for
   qtile for five years

Signed-off-by: Tycho Andersen <6b523322678240882acbb4da5312a12d8cd0082d@tycho.ws>

tych0/xcffib