etcdctl: add -p to ls command

This is a port of coreos/etcdctl#96
etcdctl: add --sort flag to ls command

This is a port of coreos/etcdctl#102
etcdctl: Set watch consistency to STRONG
raft: add tests for progress.maybeDecr
raft: better logging for leader transition
etcdhttp: return 404 when removing nonexistent member
Merge pull request #1492 from jonboulle/1492_nonexistent_member

Attempting to remove nonexistent member mishandled
Merge pull request #1522 from jonboulle/raft_tests

raft: add tests for progress.maybeDecr
raft: minor cleanup in comments
Merge pull request #1523 from jonboulle/raft_stuff

raft: minor cleanup in comments
Merge pull request #1526 from xiangli-cmu/leader_log

raft: better logging for leader transition
doc: add a Custom etcd discovery service section
Merge pull request #1530 from xiangli-cmu/discovery_doc

doc: add a Custom etcd discovery service section
client: test assertStatusCode
Merge pull request #1508 from bcwaldon/etcdctl-96

etcdctl: add -p to ls command
Merge pull request #1509 from bcwaldon/etcdctl-102

etcdctl: add --sort flag to ls command
*: rename initial-cluster-name to initial-cluster-token
etcdctl: remove SetConsistency call

This call to SetConsistency is explicitly setting the default
value, so it's really unnecessary.
Merge pull request #1534 from bcwaldon/client-tests

client: test assertStatusCode
etcdserver: exit program when node is removed

Originally added in 400dd2d7bce39851220899bb6d98086583e73ead,
and removed by mistake when refactor cluster.