modify process of getting forwarders address
Change nsswitch.conf for host name check.
From 1st:hosts 2nd:DNS To 1st:DNS 2nd:hosts
modify ipaddr check more strictly
add forward only option
Merge remote-tracking branch 'origin/bugfix-#185' into release-0.2.0
Merge remote-tracking branch 'origin/bugfix-#184' into release-0.2.0
Merge remote-tracking branch 'origin/bugfix-#189' into release-0.2.0