Add grpc transport (#67)

diff --git a/docs/conf.py b/docs/conf.py
index cfd452f..7b820b8 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -373,3 +373,4 @@
 # Autodoc config
 autoclass_content = 'both'
 autodoc_member_order = 'bysource'
+autodoc_mock_imports = ['grpc']