dep: bump golang.org/x/net/context

Move from code.google.com/p/go.net/context to
golang.org/x/net/context before bumping to latest.
dep: use vendored imports in codegangsta/cli
rafthttp: add streaming server and client
Merge pull request #1746 from yichengq/229

rafthttp: streaming server and client
wal: add a bench for write entry
etcdserver: autodetect v0.4 WALs and upgrade them to v0.5 automatically
fix import loop, add set to types, and fix comments
fix test import loop
add snapshotted integration test
Merge pull request #1760 from xiang90/wal

wal: add a bench for write entry
Fix migration to allow snapshots to have the right IDs
Merge pull request #1743 from barakmich/auto_upgrade

etcdserver: autodetect v0.4 WALs and upgrade them to v0.5 automatically
Merge pull request #1755 from bcwaldon/golang.org-deps

Switch to golang.org/x/net/context
raft: should not decrease match and next when handling out of order msgAppResp
rafthttp: fix import
Merge pull request #1762 from xiang90/fix_import

rafthttp: fix import
Merge pull request #1761 from xiang90/fix_raft

raft: should not decrease match and next when handling out of order msgAppResp
Merge remote-tracking branch 'coreos/master' into merge

* coreos/master:
  rafthttp: fix import
  raft: should not decrease match and next when handling out of order msgAppResp
  Fix migration to allow snapshots to have the right IDs
  add snapshotted integration test
  fix test import loop
  fix import loop, add set to types, and fix comments
  etcdserver: autodetect v0.4 WALs and upgrade them to v0.5 automatically
  wal: add a bench for write entry
  rafthttp: add streaming server and client
  dep: use vendored imports in codegangsta/cli
  dep: bump golang.org/x/net/context

Conflicts:
	etcdserver/server.go
	etcdserver/server_test.go
	migrate/snapshot.go
Fix TestSlowNodeRestore