tox is already doing the job

.travis.yml

 language: python
 python:
-  - 2.6
   - 2.7
 install: pip install tox --use-mirrors
 script: tox -e py26-1.2.X,py27-1.2.X,py26-1.3.X,py27-1.3.X,py26,py27,docs