Update changelog

(cherry picked from commit 30dc95fa78)

CHANGELOG.md

@@ -1,3 +1,24 @@
+## v1.8 [unreleased]
+
+### Release Notes
+
+### New Inputs
+
+- [tengine](./plugins/inputs/tengine/README.md) - Contirbuted by @ertaoxu
+
+### Features
+
+- [#4236](https://github.com/influxdata/telegraf/pull/4236): Add SSL/TLS support to redis input.
+- [#4160](https://github.com/influxdata/telegraf/pull/4160): Add tengine input plugin.
+- [#4262](https://github.com/influxdata/telegraf/pull/4262): Add power draw field to nvidia_smi plugin.
+- [#4271](https://github.com/influxdata/telegraf/pull/4271): Add support for solr 7 to the solr input.
+
+## v1.7.1 [unreleased]
+
+### Bugfixes
+
+- [#4277](https://github.com/influxdata/telegraf/pull/4277): Treat sigterm as a clean shutdown signal.
+
 ## v1.7 [2018-06-12]
 
 ### Release Notes