use tox without the .travis-runtox script

.travis.yml

@@ -1,17 +1,18 @@
 language: python
+python: 2.7
+env:
+  - TOX_ENV=py26
+  - TOX_ENV=py27
+  - TOX_ENV=py32
+  - TOX_ENV=py33
+  - TOX_ENV=pypy
 
-python:
-  - 2.6
-  - 2.7
-  - 3.2
-  - pypy
+install:
+  - pip install tox
 
-before_install: pip install --use-mirrors tox
-
-install: python setup.py install
-script: ./.travis-runtox.py
+script:
+  - tox -e $TOX_ENV
 
 branches:
   except:
     - standalone
-