add forgotten python-memcached

requirements.in

@@ -2,4 +2,5 @@ ndh
 django-filter
 django-tables2
 gitpython
+python-memcached
 requests

requirements.txt

@@ -14,8 +14,10 @@ gitdb2==2.0.3             # via gitpython
 gitpython==2.1.8
 idna==2.6                 # via requests
 ndh==3.2.1
+python-memcached==1.59
 pytz==2018.3              # via django
 requests==2.18.4
+six==1.11.0               # via python-memcached
 smmap2==2.0.3             # via gitdb2
 urllib3==1.22             # via requests
 https://github.com/jieter/django-tables2/archive/two.zip