chore(client): update python-dateutil to 2.4.1

See https://github.com/dateutil/dateutil/releases/tag/2.4.1

Author: mboersma

dev_requirements.txt

@@ -1,6 +1,6 @@
 # Deis client requirements
 docopt==0.6.2
-python-dateutil==2.4.0
+python-dateutil==2.4.1
 requests==2.5.1
 termcolor==1.1.0