Document the _proto directory (#4756)

Signed-off-by: Timothy Hobbs <timothy@hobbs.cz>

_proto/README.md

@@ -0,0 +1,10 @@
+Protobuf3 type declarations for the Helm API
+--------------------------------------------
+
+Packages
+
+ - `hapi.chart` Complete serialization of Heml charts
+ - `hapi.release` Information about installed charts (Releases) such as metadata about when they were installed, their status, and how they were configured.
+ - `hapi.services.rudder` Definition for the ReleaseModuleService used by Tiller to manipulate releases on a given node
+ - `hapi.services.tiller` Definition of the ReleaseService provoded by Tiller and used by Helm clients to manipulate releases cluster wide.
+ - `hapi.version` Version meta-data used by tiller to express it's version