Remove jingo for 1.8.

Tests don't even run without this:

File "django-compressor/.tox/py27-1.8.X/lib/python2.7/site-packages/jingo/__init__.py", line 12, in <module>
    from django.template.context import get_standard_processors
ImportError: cannot import name get_standard_processors

compressor/test_settings.py

@@ -21,8 +21,9 @@ DATABASES = {
 INSTALLED_APPS = [
     'compressor',
     'coffin',
-    'jingo',
 ]
+if django.VERSION < (1, 8):
+    INSTALLED_APPS.append('jingo')
 
 STATIC_URL = '/static/'