* types.NewCommit

* use types.NewCommit everywhere

* fix log in unsafe_reset

* memoize height and round in constructor

* notes about deprecating toVote

* bring back memoizeHeightRound

* types: memoize height/round in commit instead of first vote

* types: commit.ValidateBasic in VerifyCommit

* types: new CommitSig alias for Vote

In preparation for reducing the redundancy in Commits, we introduce the
CommitSig as an alias for Vote. This is non-breaking on the protocol,
and minor breaking on the Go API, as Commit now contains a list of
CommitSig instead of Vote.

* remove dependence on ToVote

* update some comments

* fix tests

* fix tests

* fixes from review

* Begin simple merkle compatibility PR

* Fix query_test

* Use trillian test vectors

* Change the split point per RFC 6962

* update spec

* refactor innerhash to match spec

* Update changelog

* Address @liamsi's comments

* Write the comment requested by @liamsi

* fix fastsync may stuck by a wrong block

* fixes from updates

* fixes from review

* Align spec with the changes

* fmt

* Implement BFT time

* set LastValidators when creating state in state helper

for heights >= 2

make BlockMeta Header a non-pointer

Refs #693

This reverts commit d02c5d1e30.

Also, fix consensus liveness issue.

This reverts commit 96a3502

NOTE we only updating for tmlibs and abci

Fixes:

```
panic: Panicked on a Sanity Check: can't encode times below 1970 [recovered]
        panic: Panicked on a Sanity Check: can't encode times below 1970

goroutine 2042 [running]:
testing.tRunner.func1(0xc420e8c0f0)
        /usr/local/go/src/testing/testing.go:711 +0x5d9
panic(0xcd9e20, 0xc420c8c270)
        /usr/local/go/src/runtime/panic.go:491 +0x2a2
github.com/tendermint/tendermint/vendor/github.com/tendermint/tmlibs/common.PanicSanity(0xcd9e20, 0xf8ddd0)
        /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/tmlibs/common/errors.go:26 +0x120
github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire.WriteTime(0x0, 0x0, 0x0, 0x1306440, 0xc4201607e0, 0xc420e31658, 0xc420e31680)
        /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire/time.go:19 +0x11e
github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire.writeReflectBinary(0xdc9e40, 0xc4201fcf30, 0x199, 0x1317b80, 0xdc9e40, 0xc98451, 0x9, 0x0, 0xdc9e40, 0xc420ead9c0, ...)
        /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire/reflect.go:525 +0x22f0
github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire.writeReflectBinary(0xd25400, 0xc42000e2e8, 0x196, 0x1317b80, 0xd92d60, 0xc9a195, 0xa, 0x0, 0xcc8ce0, 0xc420164920, ...)
        /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire/reflect.go:530 +0x21e7
github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire.writeReflectBinary(0xcc8ce0, 0xc4209f95b8, 0x197, 0x1317b80, 0xcc8ce0, 0xc9a195, 0xa, 0x0, 0xcc8ce0, 0xc420164920, ...)
        /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire/reflect.go:518 +0x2509
github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire.writeReflectBinary(0xd873e0, 0xc4209f9580, 0x16, 0x1317b80, 0xd79400, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire/reflect.go:530 +0x21e7
github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire.WriteBinary(0xd873e0, 0xc4209f9580, 0x1306440, 0xc4201607e0, 0xc420e31658, 0xc420e31680)
        /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire/wire.go:80 +0x15f
github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire.BinaryBytes(0xd873e0, 0xc4209f9580, 0x3, 0x8, 0xc420160798)
        /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/go-wire/util.go:15 +0xb8
github.com/tendermint/tendermint/blockchain.(*BlockStore).SaveBlock(0xc4201342a0, 0xc420eac180, 0xc420130640, 0xc4209f9580)
        github.com/tendermint/tendermint/blockchain/_test/_obj_test/store.go:192 +0x439
github.com/tendermint/tendermint/blockchain.TestBlockStoreSaveLoadBlock(0xc420e8c0f0)
        /go/src/github.com/tendermint/tendermint/blockchain/store_test.go:128 +0x609
testing.tRunner(0xc420e8c0f0, 0xf20830)
        /usr/local/go/src/testing/testing.go:746 +0x16d
created by testing.(*T).Run
        /usr/local/go/src/testing/testing.go:789 +0x569
exit status 2
FAIL
```

With feedback from @ebuchman, to make the tests nicer
and less fragile.

Add tests to test store, to the fullest reasonable extent for
paths that can taken by input arguments altering internal behavior,
as well as by mutating content in the DB.