Add testing for all supported Python and Django versions

Document all supported versions in PyPI using trove classifiers.
Alphabetize classifiers.

Add all supported versions to tox.ini for easy testing. Tidy up tox.ini
by removing defaults for basepython.

Add all supported versions to the Travis CI configuration for CI
testing.

Use Tox-Travis to help build the test matrix as the different versions
of Django do not have complete overlap of Python support.

Update Travis configuration to use built in pip caching support.

https://docs.travis-ci.com/user/caching/#pip-cache

.travis.yml

@@ -1,33 +1,15 @@
 sudo: false
 language: python
-python: 3.5
-cache:
-  directories:
-  - "$HOME/.cache/pip"
-install:
-- pip install tox
-env:
-  - TOXENV=py27-django-18
-  - TOXENV=py27-django-19
-  - TOXENV=py27-django-110
-  - TOXENV=py27-django-111
-  - TOXENV=py35-django-18
-  - TOXENV=py35-django-19
-  - TOXENV=py35-django-110
-  - TOXENV=py35-django-111
-  - TOXENV=py35-django-master
-  - TOXENV=pypy-django-18
-  - TOXENV=pypy-django-19
-  - TOXENV=pypy-django-110
-  - TOXENV=pypy-django-111
-matrix:
-  include:
-    - python: 3.6
-      env: TOXENV=py36-django-111
-  allow_failures:
-    - env: TOXENV=py35-django-master
-script:
-- tox
+cache: pip
+python:
+  - 2.7
+  - 3.3
+  - 3.4
+  - 3.5
+  - 3.6
+  - pypy
+install: pip install tox-travis
+script: tox
 deploy:
   provider: pypi
   user: jazzband
@@ -37,4 +19,4 @@ deploy:
   on:
     tags: true
     repo: jazzband/django-constance
-    condition: "$TOXENV = py27-django-18"
+    python: 3.6

setup.py

@@ -34,19 +34,24 @@ setup(
         'Development Status :: 5 - Production/Stable',
         'Environment :: Web Environment',
         'Framework :: Django',
+        'Framework :: Django :: 1.8',
+        'Framework :: Django :: 1.9',
+        'Framework :: Django :: 1.10',
+        'Framework :: Django :: 1.11',
         'Intended Audience :: Developers',
-        'Natural Language :: English',
         'License :: OSI Approved :: BSD License',
+        'Natural Language :: English',
         'Operating System :: OS Independent',
         'Programming Language :: Python',
         'Programming Language :: Python :: 2',
-        'Programming Language :: Python :: 2.6',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.2',
         'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: Implementation :: CPython',
+        'Programming Language :: Python :: Implementation :: PyPy',
         'Topic :: Utilities',
     ],
     packages=find_packages(exclude=['tests', 'tests.*']),

tox.ini

@@ -1,14 +1,12 @@
 [tox]
 envlist =
-    {py27,py35,py36,pypy}-django-{18,19,110,111}
-    {py35}-django-master
+    py{27,33,34,35,py}-django-18
+    py{27,34,35,py}-django-19
+    py{27,34,35,py}-django-110
+    py{27,34,35,36,py}-django-111
+    py{34,35,36}-django-master
 
 [testenv]
-basepython =
-    py27: python2.7
-    py35: python3.5
-    py36: python3.6
-    pypy: pypy
 deps =
     redis
     coverage
@@ -19,9 +17,11 @@ deps =
     django-110: Django>=1.10,<1.11
     django-111: Django>=1.11,<2.0
     django-master: https://github.com/django/django/archive/master.tar.gz
-usedevelop = true
+usedevelop = True
+ignore_outcome =
+    django-master: True
 commands =
-    coverage run {envbindir}/django-admin.py test -v2
+    coverage run {envbindir}/django-admin test -v2
     coverage report
 setenv =
     PYTHONDONTWRITEBYTECODE=1