add missing Timestamp to Votes
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
```
8fc7d63cf8