Update pytz from 2018.4 to 2018.5

pyup-bot · pyup-bot · commit 446201a88a19 · 2018-06-29T08:18:52.000+01:00
diff --git a/requirements.txt b/requirements.txt
@@ -1,5 +1,5 @@
 pillow==5.1.0  # Image library.
-pytz==2018.4
+pytz==2018.5
 requests-mock==1.5.0  # Mock `requests`.
 requests==2.19.1
 wrapt==1.10.11  # Make better decorators.
