Use tar.gz instead of zip to work around an encoding issue in pip's u…

…npacker.

tox.ini

@@ -23,12 +23,12 @@ setenv =
     DJANGO_CONFIGURATION = Test
 deps =
     -rtests/requirements.txt
-    dj14: https://github.com/django/django/archive/stable/1.4.x.zip#egg=django
-    dj15: https://github.com/django/django/archive/stable/1.5.x.zip#egg=django
-    dj16: https://github.com/django/django/archive/stable/1.6.x.zip#egg=django
-    dj17: https://github.com/django/django/archive/stable/1.7.x.zip#egg=django
-    dj18: https://github.com/django/django/archive/stable/1.8.x.zip#egg=django
-    dj19: https://github.com/django/django/archive/master.zip#egg=django
+    dj14: https://github.com/django/django/archive/stable/1.4.x.tar.gz#egg=django
+    dj15: https://github.com/django/django/archive/stable/1.5.x.tar.gz#egg=django
+    dj16: https://github.com/django/django/archive/stable/1.6.x.tar.gz#egg=django
+    dj17: https://github.com/django/django/archive/stable/1.7.x.tar.gz#egg=django
+    dj18: https://github.com/django/django/archive/stable/1.8.x.tar.gz#egg=django
+    dj19: https://github.com/django/django/archive/master.tar.gz#egg=django
 
 commands =
     coverage run {envbindir}/django-cadmin test -v2 {posargs:tests}