Fix the tox to install the right requirements

tox.ini

@@ -6,10 +6,25 @@ skipsdist = True
 usedevelop = True
 install_command = pip install {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
-deps = -r{toxinidir}/requirements.txt
-       -r{toxinidir}/test-requirements.txt
+deps = -r{toxinidir}/test-requirements.txt
 commands = nosetests {posargs}
 
+[testenv:py27]
+deps = {[testenv]deps}
+    -r{toxinidir}/requirements-py2.txt
+
+[testenv:py26]
+deps = {[testenv]deps}
+    -r{toxinidir}/requirements-py2.txt
+
+[testenv:py33]
+deps = {[testenv]deps}
+    -r{toxinidir}/requirements-py3.txt
+
+[testenv:py34]
+deps = {[testenv]deps}
+    -r{toxinidir}/requirements-py3.txt
+
 [testenv:pep8]
 commands = flake8 {posargs}