add docs badge to readme

README.md

@@ -2,6 +2,7 @@
 <p align="center">
     <a href="https://circleci.com/gh/vapor-ware/synse-server"><img src="https://circleci.com/gh/vapor-ware/synse-server.svg?style=shield"></a>
     <a href="https://codecov.io/gh/vapor-ware/synse-server"><img src="https://codecov.io/gh/vapor-ware/synse-server/branch/master/graph/badge.svg" /></a>
+    <a href='http://synse-server.readthedocs.io/en/latest/?badge=latest'><img src='https://readthedocs.org/projects/synse-server/badge/?version=latest' alt='Documentation Status' /></a>
         
 <h1 align="center">Synse Server</h1>
 </p>
@@ -399,4 +400,4 @@ Synse is released under GPLv2 - see [LICENSE](LICENSE) for more information.
 [example-deployment]: https://github.com/vapor-ware/synse-emulator-plugin/tree/master/deploy/docker
 
 [tox]: https://tox.readthedocs.io/en/latest/
-[grpc]: https://grpc.io/
+[grpc]: https://grpc.io/