Merge pull request #109 from coreos/upstream

Update
Use os.File.Sync.
Merge pull request #111 from mattn/windows

Build on windows
Merge pull request #110 from coreos/conf

Conf
Minor refactor of AddPeer/RemovePeer.
Merge pull request #112 from goraft/minor-refactor-add-remove-peer

Minor refactor of AddPeer/RemovePeer.
Merge pull request #113 from coreos/upstream

check sendSRR response
chore(server): spelling error

s/connectiongString/connectionString/
Merge https://github.com/goraft/raft into upstream