Claim Python 3.4 support

Tests with Python 3.4 passed on Travis, for a bit.
Add a tox.ini

This simplifies testing all Python versions to 'tox'.

Unfortunately detox cannot be used to run the tests in parallel since
dev.py scribbles directly into the top-level of the source tree (in
bin/).
Fix test failures introduced in 067acf75397

PKG-INFO for setuptools 3.3 has non-ASCII characters.  This causes
two test failures on Python 2, one of them rather unobvious
(testing_bugfix.txt complains about the different number of logging
handlers, of all things).