chore(server/transporter): set RequestTimout reasonable
chore(config): reset retry interval

Make retry interval random one to avoid join collision.
chore(etcd): loose request timeout

This is a hack to improve multi-etcd boot process.
It could make users alwasy start etcd cluster successfully.
chore(server/transporter): remove unnecessary timeout
Merge pull request #734 from unihorn/67

chore: gofmt go files
fix(server): rejoin cluster with different ip
docs(clustering): docs about rejoin
tests(rejoin): add TestReplaceWithDifferentPeerAddress

The functionality has not been implemented yet.
Merge pull request #643 from unihorn/45

fix(server): rejoin cluster with different ip
Merge pull request #624 from unihorn/36

chore(server/transporter): set RequestTimout reasonable
docs(upgrade): instructions for upgrade to v0.4