Bump python-memcached from 1.48 to 1.59

Bumps [python-memcached](https://github.com/linsomniac/python-memcached) from 1.48 to 1.59.
- [Release notes](https://github.com/linsomniac/python-memcached/releases)
- [Changelog](https://github.com/linsomniac/python-memcached/blob/master/ChangeLog)
- [Commits](https://github.com/linsomniac/python-memcached/commits/1.59)

Signed-off-by: dependabot[bot] <support@dependabot.com>

requirements.txt

@@ -22,7 +22,7 @@ mysql-python==1.2.5
 newrelic==3.2.2.94
 path.py==11.0.1
 python-dateutil==2.7.3    # via botocore
-python-memcached==1.48
+python-memcached==1.59
 python-termstyle==0.1.10
 pytz==2018.4
 pyyaml==3.12              # via edx-django-release-util

requirements/base.in

@@ -10,7 +10,7 @@ gunicorn==0.16.1
 isort
 newrelic
 path.py==11.0.1
-python-memcached==1.48
+python-memcached==1.59
 python-termstyle==0.1.10
 pytz
 requests