Update urllib3 from 1.21.1 to 1.22

Author: pyup-bot

requirements_dev.txt

@@ -31,7 +31,7 @@ Sphinx==1.6.3
 sphinx-rtd-theme==0.2.4
 sphinxcontrib-websupport==1.0.1
 tox==2.7.0
-urllib3==1.21.1
+urllib3==1.22
 virtualenv==15.1.0
 watchdog==0.8.3          # required by watchmedo
 whichcraft==0.4.1