Allow watch on etcd root
Merge pull request #58 from 3XX0/watch-root

Allow watch on etcd root
refactor use keyToPath to generate path for the key
feat(dir) add dir releated functions
Merge pull request #62 from xiangli-cmu/add_dir_func

Add dir func
feat(response.go) return etcd,raft index and raft term
Merge pull request #65 from xiangli-cmu/add_index

feat(response.go) return etcd,raft index and raft term
feat(error.go) add a not reachable error type
Merge pull request #67 from xiangli-cmu/add_notReachable_errorType

feat(error.go) add a not reachable error type