simplify Tox file and sinc it with versions in .travis.yml

tox.ini

@@ -5,108 +5,20 @@ exclude = .tox,docs/modeltranslation/conf.py
 [tox]
 distribute = False
 envlist =
-    py36-1.11.X,
-    py35-1.11.X,
-    py34-1.11.X,
-    py27-1.11.X,
-    py35-1.10.X,
-    py34-1.10.X,
-    py27-1.10.X,
-    py35-1.9.X,
-    py34-1.9.X,
-    py27-1.9.X,
-    py35-1.8.X,
-    py34-1.8.X,
-    py33-1.8.X,
-    py27-1.8.X,
+    py{27,34,35,36}-1.11.X,
+    py{34,35,36}-2.0.X,
 
 [testenv]
 downloadcache = {toxworkdir}/_download/
 commands =
     django-admin.py --version
     {envpython} runtests.py
-
-
-[testenv:py36-1.11.X]
-basepython = python3.6
-deps =
-    Django>=1.11,<1.12
-    Pillow
-
-[testenv:py35-1.11.X]
-basepython = python3.5
-deps =
-    Django>=1.11,<1.12
-    Pillow
-
-[testenv:py34-1.11.X]
-basepython = python3.4
-deps =
-    Django>=1.11,<1.12
-    Pillow
-
-[testenv:py27-1.11.X]
-basepython = python2.7
-deps =
-    Django>=1.11,<1.12
-    Pillow
-
-[testenv:py35-1.10.X]
-basepython = python3.5
-deps =
-    Django>=1.10,<1.11
-    Pillow
-
-[testenv:py34-1.10.X]
-basepython = python3.4
-deps =
-    Django>=1.10,<1.11
-    Pillow
-
-[testenv:py27-1.10.X]
-basepython = python2.7
-deps =
-    Django>=1.10,<1.11
-    Pillow
-
-[testenv:py35-1.9.X]
-basepython = python3.5
-deps =
-    Django>=1.9,<1.10
-    Pillow
-
-[testenv:py34-1.9.X]
-basepython = python3.4
-deps =
-    Django>=1.9,<1.10
-    Pillow
-
-[testenv:py27-1.9.X]
-basepython = python2.7
-deps =
-    Django>=1.9,<1.10
-    Pillow
-
-[testenv:py35-1.8.X]
-basepython = python3.5
-deps =
-    Django>=1.8,<1.9
-    Pillow
-
-[testenv:py34-1.8.X]
-basepython = python3.4
-deps =
-    Django>=1.8,<1.9
-    Pillow
-
-[testenv:py33-1.8.X]
-basepython = python3.3
-deps =
-    Django>=1.8,<1.9
-    Pillow
-
-[testenv:py27-1.8.X]
-basepython = python2.7
-deps =
-    Django>=1.8,<1.9
+basepython =
+    py27: python2.7
+    py34: python3.4
+    py35: python3.5
+    py36: python3.6
+deps =
+    1.11.X: Django==1.11.*
+    2.0.X: Django==2.0.*
     Pillow