Drop Python 3.4 support

requirements/testproj.txt

@@ -2,7 +2,7 @@
 Pillow>=4.3.0
 django-cors-headers>=2.1.0
 django-filter>=1.1.0,<2.0; python_version == "2.7"
-django-filter>=1.1.0; python_version >= "3.4"
+django-filter>=1.1.0; python_version >= "3.5"
 djangorestframework-camel-case>=0.2.0
 djangorestframework-recursive>=0.1.2
 dj-database-url>=0.4.2