move travis testing to tox

.travis.yml

@@ -1,11 +1,15 @@
+sudo: false
+cache:
+  directories:
+    - .tox
 language: python
-python:
-    - 2.6
-    - 2.7
-    - 3.3
+env:
+    - TOXENV=py26
+    - TOXENV=py27
+    - TOXENV=py33
 install:
-    - pip install .
+    - travis_retry pip install tox
 script:
-    - python setup.py test -q
+    - tox
 notifications:
     email: false

tox.ini

@@ -0,0 +1,12 @@
+[tox]
+envlist =
+    py26,py27,py33
+
+[testenv]
+commands =
+    python setup.py test -q
+# without explicit deps, setup.py test will download a bunch of eggs into $PWD
+# (and it seems I can't use zope.dottedname[testing] here, so forget DRY)
+deps =
+    zope.interface
+    zope.schema