Add urllib3 AuthorizedHttp (#19)

diff --git a/docs/conf.py b/docs/conf.py
index ccd864a..b70918f 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -363,7 +363,10 @@
 
 
 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'https://docs.python.org/3.5': None}
+intersphinx_mapping = {
+    'python': ('https://docs.python.org/3.5', None),
+    'urllib3': ('https://urllib3.readthedocs.io/en/latest', None),
+}
 
 # Autodoc config
 autoclass_content = 'both'