modernize tox.ini a bit and make another test dict-ordering independent

tox.ini

@@ -1,10 +1,10 @@
 [tox]
-envlist=py26,py32,py33,py34,py27,py27-pexpect,py33-pexpect,py26,py26-old,py33-old,flakes
+envlist=py26,py33,py34,py27,py27-pexpect,py33-pexpect,py26,py26-old,py33-old,flakes
 
 [testenv]
 changedir=testing
 deps=pytest>=2.5.1
-commands= py.test --junitxml={envlogdir}/junit-{envname}.xml []
+commands= py.test {posargs}
 
 [testenv:py27-pexpect]
 deps={[testenv]deps}
@@ -19,13 +19,24 @@ deps = pytest-flakes>=0.2
 commands = py.test --flakes -m flakes testing xdist
 
 [testenv:py26-old]
+basepython = python2.6
 deps=
-    pytest==2.4.2
+    pytest==2.5.2
+    pycmd
+
+commands= 
+    py.cleanup -a
+    py.test {posargs}
 
 [testenv:py33-old]
 basepython = python3.3
 deps=
-    pytest==2.4.2
+    pytest==2.5.2
+    pycmd
+
+commands= 
+    py.cleanup -a
+    py.test {posargs}
 
 [pytest]
 addopts = -rsfxX