etcd 操作sdk

不区分etcd api版本统一实现接口，方便应用层调用

Name		Name	Last commit message	Last commit date
Latest commit History 12 Commits
etcdv2		etcdv2
etcdv3		etcdv3
model		model
LICENSE		LICENSE
README.md		README.md
etcdsdk.go		etcdsdk.go

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