Change install_requires to not require Django

Author: PamelaM

django_coverage_plugin/plugin.py

@@ -78,6 +78,10 @@ def check_debug():
     return True
 
 
+if django.VERSION < (1, 8):
+    raise RuntimeError("Django Coverage Plugin requires Django 1.8 or higher")
+
+
 if django.VERSION >= (1, 9):
     # Since we are grabbing at internal details, we have to adapt as they
     # change over versions.

setup.py

@@ -29,7 +29,6 @@
     url='https://github.com/nedbat/django_coverage_plugin',
     packages=['django_coverage_plugin'],
     install_requires=[
-        'Django >= 1.8',
         'coverage >= 4.0',
         'six >= 1.4.0',
     ],