Update to work with more recent colormath.

Color distances now have to be explicitly done via a conversion to Lab space.
Python 3 compatibility changes.
Update trove classifiers for Python 3.
Also test on Python 3.4.
Simplify TravisCI build step.
s/iteritems/items/g
Fix test for virtualenv.
Update test to match current output :P

Changes in colormath have lead to a smaller selection of colors in the Ares
logo palette. It's difficult to debug why we have two few fewer colors.
Accepting this result for now.
Drop unofficial Python 2.6 support.

Before this branch, setup.py would abort on any Python version other than 2.7
anyway. Since our test runner no longer works on 2.6, we drop support here.