*: fix Procfile
*: print out configuration when necessary
etcdserver: fix server.Stop()

Stop should be idempotent. It should simply send a stop signal to the server.
It is the server's responsibility to stop the go-routines and related components.
etcdserver: validate new node is not registered before in best effort
Merge pull request #1713 from xiang90/stop

etcdserver: fix server.Stop()
etcdserver: minor cleanup
etcdserver: fix TestDoProposalStopped test

We start etcd server in this test without the cluster. Sometimes it panics when
accessing the cluster. Most of the time it does not panic, since we can stop the
server fast enough before applying the first configuration change entry.
etcdserver: add StopNotify
Merge pull request #1708 from yichengq/223

etcdserver: validate new node is not registered before in best effort
Merge pull request #1704 from xiang90/print_config

*: print out configuration when necessary
Merge pull request #1714 from xiang90/stop

StopNotify
sender: support elegant stop
Merge pull request #1718 from yichengq/226

sender: support elegant stop
Merge pull request #1703 from jonboulle/proc

*: fix Procfile
raft: not set applied when restored from snapshot

applied is only updated by application level through Advance.
etcdserver: recover from snapshot before applying requests
etcdserver: check and select committed entries to apply
etcdserver: recover cluster when receiving newer snapshot
Merge pull request #1719 from yichengq/228

etcdserver: recover snapshot before applying committed entries
etcdserver: export Member.StoreKey