Release v1.6.0 (#324)

* Update version and changelog for v1.6.0
* Update docs
diff --git a/docs/epy/googleapiclient.discovery-module.html b/docs/epy/googleapiclient.discovery-module.html
index 009d36e..cb8ac4a 100644
--- a/docs/epy/googleapiclient.discovery-module.html
+++ b/docs/epy/googleapiclient.discovery-module.html
@@ -643,7 +643,8 @@
   model: googleapiclient.Model, converts to and from the wire format.
   requestBuilder: googleapiclient.http.HttpRequest, encapsulator for an HTTP
     request.
-  credentials: oauth2client.Credentials, credentials to be used for
+  credentials: oauth2client.Credentials or
+    google.auth.credentials.Credentials, credentials to be used for
     authentication.
   cache_discovery: Boolean, whether or not to cache the discovery doc.
   cache: googleapiclient.discovery_cache.base.CacheBase, an optional
@@ -739,7 +740,9 @@
   model: Model class instance that serializes and de-serializes requests and
     responses.
   requestBuilder: Takes an http request and packages it up to be executed.
-  credentials: object, credentials to be used for authentication.
+  credentials: oauth2client.Credentials or
+    google.auth.credentials.Credentials, credentials to be used for
+    authentication.
 
 Returns:
   A Resource object with methods for interacting with the service.
@@ -1250,7 +1253,7 @@
 <table border="0" cellpadding="0" cellspacing="0" width="100%%">
   <tr>
     <td align="left" class="footer">
-    Generated by Epydoc 3.0.1 on Tue Nov  1 17:02:49 2016
+    Generated by Epydoc 3.0.1 on Thu Jan  5 12:55:02 2017
     </td>
     <td align="right" class="footer">
       <a target="mainFrame" href="http://epydoc.sourceforge.net"