Import DiscoverRunner for django 1.8 support

This is the same way that django-nose imports DiscoverRunner and
falls back to DjangoTestSuiteRunner on older versions of django.

refs jpellerin#2

djnose2/runner.py

@@ -4,13 +4,18 @@
 import logging
 
 from django.test import simple
+try:
+    from django.test.runner import DiscoverRunner
+except ImportError:
+    # Django < 1.8
+    from django.test.simple import DjangoTestSuiteRunner as DiscoverRunner
 from nose2.main import discover
 
 
 log = logging.getLogger(__name__)
 
 
-class TestRunner(simple.DjangoTestSuiteRunner):
+class TestRunner(DiscoverRunner):
 
     err_count = 0
     _hooks = ('startTestRun', 'reportFailure', 'reportError')