Update pytz from 2018.9 to 2019.1

Author: pyup-bot

requirements.txt

@@ -11,7 +11,7 @@ numpy==1.16.0
 pandas==0.24.2
 pyquery==1.4.0
 python-dateutil==2.7.5
-pytz==2018.9
+pytz==2019.1
 requests==2.21.0
 six==1.12.0
 soupsieve==1.9