Django version loosening

This commit loosens the allowable version of django to anything
<1.9a0. Each of 1.8, 1.9, and 1.10 can now be tested using tox,
which will make the eventual upgrades much easier.

.travis.yml

 language: python
 python:
   - "2.7"
+env:
+  - TOXENV=django18
+  - TOXENV=django19
+  - TOXENV=django110
+matrix:
+  allow_failures:
+    - env: TOXENV=django19
+    - env: TOXENV=django110
 # Use docker for travis builds
 sudo: false
 install:
@@ -9,7 +17,6 @@ install:
   - "python setup.py install"
   - "pip install coveralls"
 script:
-  - "python manage.py test"
-  - "python setup.py build_sphinx"
+  - "tox"
 after_success:
   coveralls

MANIFEST.in

 include requirements.txt
 include test-requirements.txt
+include tox-requirements.txt
 include LICENSE
 include AUTHORS
 include README.rst

requirements.txt

 dogapi==1.2.1
-django>=1.8.14,<1.9
 django-extensions==1.5.9
 django-model-utils==2.3.1
 # Use the same cherry-picked repo as edx-platform

setup.py

@@ -46,6 +46,6 @@ setup(
         'Programming Language :: Python',
     ],
     packages=['submissions', 'submissions.migrations'],
-    install_requires=load_requirements('requirements.txt'),
+    install_requires=load_requirements('requirements.txt', 'tox-requirements.txt'),
     tests_require=load_requirements('test-requirements.txt'),
 )

test-requirements.txt

@@ -14,3 +14,6 @@ git+https://github.com/edx/edx-lint.git@v0.4.1#egg=edx_lint==0.4.1
 Sphinx==1.2
 sphinx-rtd-theme==0.1.5
 sphinxcontrib-napoleon==0.2.3
+
+# Tox
+tox==2.6.0

tox-requirements.txt

+Django<1.11

tox.ini

+[tox]
+envlist = django{18,19,110}
+
+[testenv]
+deps =
+    -r{toxinidir}/requirements.txt
+    -r{toxinidir}/test-requirements.txt
+    django18: Django>=1.8,<1.9
+    django19: Django>=1.9,<1.10
+    django110: Django>=1.10,<1.11
+commands =
+    python manage.py test
+    python setup.py build_sphinx