Add Travis for Python 2.7 & 3.4-3.7

Moves django-contrib-comments to be an extra, so is not mandatory.
Pre-install appropriate versions of django-contrib-comments in
tox.

Closes #2

.travis.yml

@@ -0,0 +1,13 @@
+dist: xenial
+language: python
+cache: pip
+python:
+  - 2.7.13
+  - 3.4
+  - 3.5
+  - 3.6
+  - 3.7
+install:
+  - pip install tox-travis
+script:
+  - tox

setup.py

@@ -16,6 +16,12 @@ def read(fname):
 Intended Audience :: System Administrators
 License :: OSI Approved :: MIT License
 Programming Language :: Python
+Programming Language :: Python :: 2.7
+Programming Language :: Python :: 3.4
+Programming Language :: Python :: 3.5
+Programming Language :: Python :: 3.6
+Programming Language :: Python :: 3.7
+Framework :: Django
 Topic :: Software Development :: Libraries :: Python Modules
 Operating System :: Microsoft :: Windows
 Operating System :: Unix
@@ -27,6 +33,10 @@ def read(fname):
 needs_pytest = {'pytest', 'test', 'ptr'}.intersection(sys.argv)
 setup_requires = ['pytest-runner'] if needs_pytest else []
 
+extras = {
+    'comments': ['django-contrib-comments'],
+}
+
 setup(
     name='django-compat-patcher',
     version=read("VERSION"),
@@ -41,7 +51,8 @@ def read(fname):
 
     packages=packages,
 
-    install_requires=['django-contrib-comments'] + (["Django<2"] if (sys.version_info < (3,)) else []),
+    install_requires=(['Django<2'] if (sys.version_info < (3,)) else ['Django']),
+    extras_require=extras,
     setup_requires=setup_requires,
     tests_require=["pytest", "pytest-pythonpath", "django-compat"],
 

tox.ini

@@ -16,9 +16,12 @@ deps=
     django2_0: Django>=2,<2.1
     django2_1: Django>=2.1,<2.2
     django2_2: Django>=2.2,<3.0
+
+    django1_{8,9,10}: django-contrib-comments==1.7.0
+    django1_11,django2_{0,1,2}: django-contrib-comments>=1.8.0
 commands=
-        python {toxinidir}/setup.py test
-        python check_behaviour_with_minimal_settings.py
+    python {toxinidir}/setup.py test
+    python check_behaviour_with_minimal_settings.py
 
 #[testenv:doc]
 ## see http://tox.readthedocs.io/en/latest/example/general.html#integrating-sphinx-documentation-checks