Simpler dependency management

Author: nedbat

requirements.txt

@@ -1,5 +1,2 @@
-# If you change this file, don't forget to update tox.ini and setup.py also.
-coverage >= 4.0b2
-Django >= 1.4
-six >= 1.4.0
+# To run tests, we just need tox.
 tox >= 1.8

setup.py

@@ -11,7 +11,6 @@
     url='https://github.com/nedbat/django_coverage_plugin',
     packages=['django_coverage_plugin'],
     install_requires=[
-        # If you change this, update tox.ini and requirements.txt also.
         'Django >= 1.4',
         'coverage >= 4.0b2',
         'six >= 1.4.0',

tox.ini

@@ -13,15 +13,12 @@
 envlist = py{27,34}-django{14,15,16,17,18},check
 
 [testenv]
-# Keep these dependencies in sync with the requirements.txt file.
 deps =
     django14: Django >=1.4, <1.5
     django15: Django >=1.5, <1.6
     django16: Django >=1.6, <1.7
     django17: Django >=1.7, <1.8
     django18: Django >=1.8, <1.9
-    six >= 1.4.0
-    coverage >= 4.0b2
 
 commands =
     {envpython} -c "import tests.banner"