Release v1.6.0 (#324)

* Update version and changelog for v1.6.0
* Update docs
diff --git a/docs/epy/toc.html b/docs/epy/toc.html
index d667889..019e619 100644
--- a/docs/epy/toc.html
+++ b/docs/epy/toc.html
@@ -16,7 +16,10 @@
   <br />
   <h2 class="toc">Modules</h2>
     <a target="moduleFrame" href="toc-googleapiclient-module.html"
-     onclick="setFrame('toc-googleapiclient-module.html','googleapiclient-module.html');"     >googleapiclient</a><br />    <a target="moduleFrame" href="toc-googleapiclient.channel-module.html"
+     onclick="setFrame('toc-googleapiclient-module.html','googleapiclient-module.html');"     >googleapiclient</a><br />  <div class="private">
+    <a target="moduleFrame" href="toc-googleapiclient._auth-module.html"
+     onclick="setFrame('toc-googleapiclient._auth-module.html','googleapiclient._auth-module.html');"     >googleapiclient._auth</a><br />  </div>
+    <a target="moduleFrame" href="toc-googleapiclient.channel-module.html"
      onclick="setFrame('toc-googleapiclient.channel-module.html','googleapiclient.channel-module.html');"     >googleapiclient.channel</a><br />    <a target="moduleFrame" href="toc-googleapiclient.discovery-module.html"
      onclick="setFrame('toc-googleapiclient.discovery-module.html','googleapiclient.discovery-module.html');"     >googleapiclient.discovery</a><br />    <a target="moduleFrame" href="toc-googleapiclient.discovery_cache-module.html"
      onclick="setFrame('toc-googleapiclient.discovery_cache-module.html','googleapiclient.discovery_cache-module.html');"     >googleapiclient.discovery_cache</a><br />    <a target="moduleFrame" href="toc-googleapiclient.discovery_cache.appengine_memcache-module.html"