Use new icon in README
-# ![](https://github.com/signalfx/integrations/blob/master/collectd-nginx-plus/img/nginx-plus-icon.png) NGINX Plus
+# ![](https://github.com/signalfx/integrations/blob/master/collectd-nginx-plus/img/integrations_nginxplus.png) NGINX Plus
_This directory consolidates all the metadata associated with the NGINX Plus plugin for collectd. The relevant code for the plugin can be found [here](https://github.com/signalfx/collectd-nginx-plus)_
