Update django and dependencies

requirements.txt

 oic==0.15.0
 pika==1.0.1
-urllib3==1.24.0
-Django==2.1.0
-djangorestframework==3.9.0
-django-cors-headers==2.5.0
-django-mysql==3.0.0.post1
+urllib3==1.25.7
+Django==2.2.7
+djangorestframework==3.10.3
+django-cors-headers==3.1.1
+django-mysql==3.2.0
 django-nose==1.4.6
-django_polymorphic==2.0.3
+django_polymorphic==2.1.2
 django-rest-polymorphic==0.1.8
-mysqlclient==1.4.2.post1
+mysqlclient==1.4.5