Release v1.6.0 (#324)

* Update version and changelog for v1.6.0
* Update docs
diff --git a/docs/epy/api-objects.txt b/docs/epy/api-objects.txt
index 935999c..c0fefaf 100644
--- a/docs/epy/api-objects.txt
+++ b/docs/epy/api-objects.txt
@@ -1,4 +1,10 @@
 googleapiclient	googleapiclient-module.html
+googleapiclient._auth	googleapiclient._auth-module.html
+googleapiclient._auth.HAS_GOOGLE_AUTH	googleapiclient._auth-module.html#HAS_GOOGLE_AUTH
+googleapiclient._auth.default_credentials	googleapiclient._auth-module.html#default_credentials
+googleapiclient._auth.with_scopes	googleapiclient._auth-module.html#with_scopes
+googleapiclient._auth.HAS_OAUTH2CLIENT	googleapiclient._auth-module.html#HAS_OAUTH2CLIENT
+googleapiclient._auth.authorized_http	googleapiclient._auth-module.html#authorized_http
 googleapiclient.channel	googleapiclient.channel-module.html
 googleapiclient.channel.CHANNEL_PARAMS	googleapiclient.channel-module.html#CHANNEL_PARAMS
 googleapiclient.channel.notification_from_headers	googleapiclient.channel-module.html#notification_from_headers