check sendSRR response
fix snapshot related issue
expose protobuf encoding/decoing API
Use os.File.Sync.
Minor refactor of AddPeer/RemovePeer.
Use github.com/coreos/go-raft import path

Rebase this patch on top of the upstream branch for keeping the coreos
go-raft paths. This is needed for the recently added protobuf
sub-package.

    git pull --rebase origin upstream
Merge pull request #1 from coreos/updateMaster

Update master