Lock the master branch at 1.11

- stay back!

requirements/base.txt

-Django>=1.11
+Django>=1.11, < 2.0
 django-crispy-forms==1.6.1
 django-ratelimit==1.0.1
 django-redis-cache==1.7.1
@@ -11,4 +11,4 @@ redis==2.10.6
 requests==2.18.4
 simplejson==3.11.1
 six
-setuptools==36.4.0
\ No newline at end of file
+setuptools==36.4.0