Revert "Add missing require for the serf module"

This reverts commit 5348fbfac65b32a3698c653c55ed1ced975e79d4.
Revert "Set cluster id as a serf tag"

This reverts commit 464c89d06eace8c45b2924b09907275a421f0da7.
Revert "Handle nodes status correctly"

This reverts commit 08d7f45e666da2cdd97d6d867f2fb6570b83aab1.
Revert "Output dead nodes also"

This reverts commit 88056ea502c61055aadbe252a6b8ec33adab9ec9.
Revert "Align"

This reverts commit 67a4292a7a43a704c8b8e55e0b13da57f4684042.
Revert "Output tags to the list of live nodes"

This reverts commit 62841ce15ff66bc826ef3b89c6ff6179a94a57a5.
Revert "Use guard unless style"

This reverts commit 38485c1de2a8d2e9aa29daaaaf1b06290103cbb2.
Revert "Add methods to modify tags"

This reverts commit 56b74997a0205c68846f545a0f79638a555bc223.
Merge branch 'master' of github.com:droonga/droonga-engine

Conflicts:
	lib/droonga/serf.rb