Follow-up to feedback from #1286, this change simplifies the connection
handling in the SocketClient and makes the communication via TCP more
robust. It introduces the tcpTimeoutListener to encapsulate accept and
i/o timeout handling as well as connection keep-alive, this type could
likely be upgraded to handle more fine-grained tuning of the tcp stack
(linger, nodelay, etc.) according to the properties we desire. The same
methods should be applied to the RemoteSigner which will be overhauled
when the priv_val_server is fleshed out.

* require private key
* simplify connect logic
* break out conn upgrades to tcpTimeoutListener
* extend test coverage and simplify component setup

Refs #1147

* expose AuthEnc in the P2P config

if AuthEnc is true, dialed peers must have a node ID in the address and
it must match the persistent pubkey from the secret handshake.

Refs #1157

* fixes after my own review

* fix docs

* fix build failure

```
p2p/pex/pex_reactor_test.go:288:88: cannot use seed.NodeInfo().NetAddress() (type *p2p.NetAddress) as type string in array or slice literal
```

* p2p: introduce peerConn to simplify peer creation

* Introduce `peerConn` containing the known fields of `peer`
* `peer` only created in `sw.addPeer` once handshake is complete and NodeInfo is checked
* Eliminates some mutable variables and makes the code flow better
* Simplifies the `newXxxPeer` funcs
* Use ID instead of PubKey where possible.
        * SetPubKeyFilter -> SetIDFilter
        * nodeInfo.Validate takes ID
        * remove peer.PubKey()

* persistent node ids

* fixes from review

* test: use ip_plus_id.sh more

* fix invalid memory panic during fast_sync test

```
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: panic: runtime error: invalid memory address or nil pointer dereference
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: [signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x98dd3e]
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]:
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: goroutine 3432 [running]:
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: github.com/tendermint/tendermint/p2p.newOutboundPeerConn(0xc423fd1380, 0xc420933e00, 0x1, 0x1239a60, 0
xc420128c40, 0x2, 0x42caf6, 0xc42001f300, 0xc422831d98, 0xc4227951c0, ...)
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: #011/go/src/github.com/tendermint/tendermint/p2p/peer.go:123 +0x31e
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: github.com/tendermint/tendermint/p2p.(*Switch).addOutboundPeerWithConfig(0xc4200ad040, 0xc423fd1380, 0
xc420933e00, 0xc423f48801, 0x28, 0x2)
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: #011/go/src/github.com/tendermint/tendermint/p2p/switch.go:455 +0x12b
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: github.com/tendermint/tendermint/p2p.(*Switch).DialPeerWithAddress(0xc4200ad040, 0xc423fd1380, 0x1, 0x
0, 0x0)
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: #011/go/src/github.com/tendermint/tendermint/p2p/switch.go:371 +0xdc
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: github.com/tendermint/tendermint/p2p.(*Switch).reconnectToPeer(0xc4200ad040, 0x123e000, 0xc42007bb00)
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: #011/go/src/github.com/tendermint/tendermint/p2p/switch.go:290 +0x25f
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: created by github.com/tendermint/tendermint/p2p.(*Switch).StopPeerForError
2018-02-21T06:30:05Z box887.localdomain docker/local_testnet_4[14907]: #011/go/src/github.com/tendermint/tendermint/p2p/switch.go:256 +0x1b7
```

Following ADDR 008 the node will connect to an external
process to handle signing requests. Operation of the external process is
left to the user.

* introduce alias for PrivValidator interface on socket client
* integrate socket client in node
* structure tests
* remove unnecessary flag

1. remove pointer
2. add Quit() method to Service interface

NOTE we only updating for tmlibs and abci

- we only use seeds if we can’t connect to peers in the addrbook.
- we always connect to nodes given in config/flags

Refs #864

we only use seeds if we can’t connect to peers in the addrbook.

Refs #864

* linter: address gosimple lints

* linter: make deterministic & a rebase fix

* lint/rpc: fix a gosimple lint

* run linter in CI

* fix rebase mistake

* fix makefile

* ugh

* revert Makefile

* add metalinter to CI

* try this

* linter: last little fix

* need glide

* better

* okayy circle, have it your way

* lints: gosimple

* pr comments