Add Django 2.1 to test targets.

Author: stephrdev

.python-version

@@ -1,5 +1,5 @@
-3.5.2
-3.4.6
-3.3.6
-2.7.12
-pypy-5.7.0
+3.6.6
+3.5.6
+3.4.9
+2.7.15
+pypy-5.7.1

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 skipsdist = True
-envlist={py27,py34,pypy}-django18,{py27,py34,py35,pypy}-django{19,110,111},{py34,py35,py36}-django20
+envlist={py27,py34,pypy}-django18,{py27,py34,py35,pypy}-django{19,110,111},{py34,py35,py36}-django20,{py35,py36}-django21
 
 [tox:travis]
 2.7 = py27
@@ -19,5 +19,6 @@ deps =
 	django110: Django>=1.10,<1.11
 	django111: Django>=1.11,<2.0
 	django20: Django>=2.0,<2.1
+	django21: Django>=2.1,<2.2
 commands =
 	py.test --cov