Release v1.6.0 (#324)

* Update version and changelog for v1.6.0
* Update docs
diff --git a/docs/epy/googleapiclient.http.BatchHttpRequest-class.html b/docs/epy/googleapiclient.http.BatchHttpRequest-class.html
index 530bcb9..a9915f9 100644
--- a/docs/epy/googleapiclient.http.BatchHttpRequest-class.html
+++ b/docs/epy/googleapiclient.http.BatchHttpRequest-class.html
@@ -59,10 +59,10 @@
 <h1 class="epydoc">Class BatchHttpRequest</h1><p class="nomargin-top"><span class="codelink"><a href="googleapiclient.http-pysrc.html#BatchHttpRequest">source&nbsp;code</a></span></p>
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@@ -740,7 +740,7 @@
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-    Generated by Epydoc 3.0.1 on Tue Nov  1 17:02:50 2016
+    Generated by Epydoc 3.0.1 on Thu Jan  5 12:55:04 2017
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