client: use all endpoints
docs: clean up clustering doc
Merge pull request #1579 from coreos/cleanup-clustering-doc

docs: clean up clustering doc
etcd: print initial cluster members during startup

etcd now prints the initial clusters members during startup.

```
2014/11/03 10:32:46 etcd: initial cluster members: etcd0=http://127.0.0.1:2380,etcd1=http://127.0.0.1:2390,etcd2=http://127.0.0.1:2400
```
Merge pull request #1570 from bcwaldon/client-endpoints

client: use all endpoints
etcdserver: panic on storage error

It is a critical error to etcd, and etcd is not able to recover it now.
Merge pull request #1478 from unihorn/190

etcdserver: panic on storage error
client: follow redirects
Merge pull request #1576 from coreos/print-initial-cluster-members

etcd: print initial cluster members during startup
Merge pull request #1571 from bcwaldon/client-redirects

client: follow redirects
wal: sync before returning from create
raft: do not load empty state and ents
raft: add paper tests for section 5.4.1
etcdserver: try to listen on ports before initializing etcd server
Merge pull request #1587 from xiangli-cmu/fix_wal

wal: sync before returning from create
etcdhttp: use EcodePrevValueRequired when appropriate
integration: add keys API integration tests
Merge pull request #1592 from jonboulle/integration_tests

integration: add keys API integration tests
etcdserver: print out initial cluster members

It is moved from etcdmain pkg because the line should only be printed out
when etcd bootstraps at the first time.
etcdhttp: always respond json-format error to client