Unify travis and tox configs

Fixes #489. Adapted from config I use on my own projects, e.g. [Django-MySQL .travis.yml](https://github.com/adamchainz/django-mysql/blob/master/.travis.yml).

.travis.yml

@@ -1,45 +1,16 @@
-language: python
-
 sudo: false
 
+language: python
+python: '3.5'
 cache: pip
 
-python:
-  - "2.7"
-  - "3.3"
-  - "3.4"
-  - "3.5"
-
-env:
-  - DJANGO='https://github.com/django/django/archive/master.tar.gz' REST_FRAMEWORK='djangorestframework>=3.4,<3.5'
-  - DJANGO="django>=1.10.0,<1.11.0" REST_FRAMEWORK="djangorestframework>=3.4,<3.5"
-  - DJANGO="django>=1.9.0,<1.10.0" REST_FRAMEWORK="djangorestframework>=3.4,<3.5"
-  - DJANGO="django>=1.8.0,<1.9.0" REST_FRAMEWORK="djangorestframework>=3.4,<3.5"
-  - DJANGO="django>=1.8.0,<1.9.0" REST_FRAMEWORK="djangorestframework>=3.3,<3.4"
-
 install:
-  - travis_retry pip install -Ur requirements/test-ci.txt
-  - travis_retry pip install $DJANGO $REST_FRAMEWORK
+  - pip install tox
 
 script:
-  - $W coverage run --source django_filters runtests.py -v 2
+  - coverage erase
+  - tox
+
+after_success:
+  - coverage combine
   - coverage report
-
-notifications:
-  email: false
-
-matrix:
-  exclude:
-    - python: "3.3"
-      env: DJANGO='https://github.com/django/django/archive/master.tar.gz' REST_FRAMEWORK='djangorestframework>=3.4,<3.5'
-    - python: "3.3"
-      env: DJANGO="django>=1.10.0,<1.11.0" REST_FRAMEWORK="djangorestframework>=3.4,<3.5"
-    - python: "3.3"
-      env: DJANGO="django>=1.9.0,<1.10.0" REST_FRAMEWORK="djangorestframework>=3.4,<3.5"
-  include:
-    - python: "3.5"
-      env: W='python -W error -m' DJANGO='https://github.com/django/django/archive/master.tar.gz' REST_FRAMEWORK='djangorestframework>=3.4,<3.5'
-  allow_failures:
-    - env: W='python -W error -m' DJANGO='https://github.com/django/django/archive/master.tar.gz' REST_FRAMEWORK='djangorestframework>=3.4,<3.5'
-    - env: DJANGO='https://github.com/django/django/archive/master.tar.gz' REST_FRAMEWORK='djangorestframework>=3.4,<3.5'
-  fast_finish: true

tox.ini

@@ -6,14 +6,7 @@ envlist =
 
 
 [testenv]
-basepython =
-             py27: python2.7
-             py33: python3.3
-             py34: python3.4
-             py35: python3.5
-
-
-commands = ./runtests.py {posargs}
+commands = coverage run --source django_filters ./runtests.py {posargs}
 setenv =
        PYTHONDONTWRITEBYTECODE=1
 deps =
@@ -24,3 +17,12 @@ deps =
     restframework33: djangorestframework>=3.3,<3.4
     restframework34: djangorestframework>=3.4,<3.5
     -rrequirements/test-ci.txt
+
+[testenv:py27-django-latest-restframework34]
+ignore_outcome = True
+
+[testenv:py34-django-latest-restframework34]
+ignore_outcome = True
+
+[testenv:py35-django-latest-restframework34]
+ignore_outcome = True