Compare Py2 vs Py3 better using comparepdf and diffpdf

Procedure:

  virtualenv -p python2.7 .
  rm bin/python
  virtualenv -p python3.4 .
  rm bin/python
  bin/python2 --version  # make sure it prints 2.7
  bin/python3 --version  # make sure it prints 3.4
  bin/python2 -m mgp2pdf -o /tmp/py2 samples/*/*.mgp --unsafe
  bin/python3 -m mgp2pdf -o /tmp/py2 samples/*/*.mgp --unsafe
  cd /tmp
  for i in py2/*.pdf; do j=${i/2/3}; comparepdf -c a $i $j || echo $i $j; done
  diffpdf py2/python3.pdf py3/python3.pdf  # for visual eyeballing

BUGS.rst

@@ -1,6 +1,7 @@
 - samples/python/python3.mgp: slide 44 is rendered wrong on Python 3,
   compared to Python 2's rendering  UHH ACTUALLY it looks like rendering
   changed in the last couple of days, current version is the same on Py2
-  vs Py3!
+  vs Py3!  Except for minor differences in text positioning, probably resulting
+  from / returning floats now
 - samples/python/python3.mgp: slide 44 is rendered wrong on Python 2,
   compared to the original PDF from 2006