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/).

.gitignore

@@ -9,3 +9,4 @@ python*/
 *.egg
 *.egg-info
 dist
+.tox

tox.ini

+[tox]
+envlist =
+    py26,py27,py32,py33
+
+[testenv]
+commands =
+    # buildout's dev.py wants python to not have setuptools
+    pip uninstall -y zc.buildout setuptools pip
+    python dev.py
+    {toxinidir}/bin/test -1 -v -c
+# since we're removing setuptools we can't possibly reuse the virtualenv
+recreate = true
+# if the user has ccache installed, PATH may contain /usr/lib/ccache that has a
+# gcc wrapper that fails to build anything when buildout's tests set HOME to a
+# non-existent directory under /tmp
+setenv =
+    PATH=/usr/bin:/bin