Add README.md for snmp input plugin

closes influxdata#735
closes influxdata#773
closes influxdata#540

CHANGELOG.md

@@ -7,13 +7,15 @@
 - [#771](https://github.com/influxdata/telegraf/pull/771): Default timeouts for input plugns. Thanks @PierreF!
 - [#758](https://github.com/influxdata/telegraf/pull/758): UDP Listener input plugin, thanks @whatyouhide!
 - [#769](https://github.com/influxdata/telegraf/issues/769): httpjson plugin: allow specifying SSL configuration.
+- [#735](https://github.com/influxdata/telegraf/pull/735): SNMP Table feature. Thanks @titilambert!
 
 ### Bugfixes
 - [#748](https://github.com/influxdata/telegraf/issues/748): Fix sensor plugin split on ":"
 - [#722](https://github.com/influxdata/telegraf/pull/722): Librato output plugin fixes. Thanks @chrusty!
 - [#745](https://github.com/influxdata/telegraf/issues/745): Fix Telegraf toml parse panic on large config files. Thanks @titilambert!
 - [#781](https://github.com/influxdata/telegraf/pull/781): Fix mqtt_consumer username not being set. Thanks @chaton78!
 - [#786](https://github.com/influxdata/telegraf/pull/786): Fix mqtt output username not being set. Thanks @msangoi!
+- [#773](https://github.com/influxdata/telegraf/issues/773): Fix duplicate measurements in snmp plugin. Thanks @titilambert!
 
 ## v0.10.4.1