removed "panic" from zfs plugin

added zfs plugin to README.md

README.md

@@ -190,6 +190,7 @@ Telegraf currently has support for collecting metrics from:
 * rabbitmq
 * redis
 * rethinkdb
+* zfs
 * zookeeper
 * system
     * cpu

plugins/zfs/zfs.go

@@ -62,7 +62,7 @@ func (z *Zfs) Gather(acc plugins.Accumulator) error {
 	for _, metric := range kstatMetrics {
 		lines, err := common.ReadLines(kstatPath + "/" + metric)
 		if err != nil {
-			panic(err)
+			return err
 		}
 		for i, line := range lines {
 			if i == 0 || i == 1 {