Add tox.ini
tox.ini: Add default option --tb=short

for shorter tracebacks
tox.ini: Include unittest2 for Python 2.6
tox.ini: Set TWIGGY_UNDER_TEST

Fixes "RuntimeError: Attempted to populate globals twice" errors
Fix test failures in tests/test_logging_compat.py

Was failing with "ImportError: cannot import name log"

because tox.ini now sets TWIGGY_UNDER_TEST

This works around that by adding setup_module and teardown_module
functions which _populate_globals and _del_globals respectively and
moving imports into test methods where they're used.
tox.ini: Don't run py.test with -v so that output is shorter
tests/test_message.py: Fix pypy test failures

Fix pypy test failures caused by fact that error message for
ZeroDivisionError in pypy is slightly different from one in CPython
Add .travis.yml
.travis.yml: Install unittest2 for Python 2.6
Merge pull request #33 from msabramo/tox

Add tox.ini for tox and .travis.yml for Travis CI