Python 3.2 not supported by coverage

[jayvdb]

As coverage now breaks on Python 3.2, something needs to change in .travis.yml.
Now is a good time to consider de-supporting Python 3.2, by removing it from both .travis.yml and setup.py.
Or, with a tiny bit of complexity, .travis.yml could avoid using coverage on Python 3.2, so it can be supported a little longer.