add variable for tags
use \t instead of \s

because each field is separated by `\t`.
like following

```
mitchellh.local    127.0.0.1    web    role=web,datacenter=east
```
Receive multilines of membership event data

When members invoke many events at once, serf send multi-line messages to stdin
like following :

one.local	192.168.0.2	one	role=one,datacenter=east
two.local	192.168.0.3	two	role=two,datacenter=south
three.local	192.168.0.4	three	role=three,datacenter=west
$role and $tags is out of use
Merge pull request #2 from tacahilo/receive-multilines-of-membership-event-data

Receive multilines of membership event data