* WIP: switching to fixed offsets for SignBytes
* add version field to sign bytes and update order
* more comments on test-cases and add a tc with a chainID
* remove amino:"write_empty" tag
- it doesn't affect if default fixed size fields ((u)int64) are
written or not
- add comment about int->int64 casting
* update CHANGELOG_PENDING
* update documentation
* add back link to issue #1622 in documentation
* remove JSON tags and add (failing test-case)
* fix failing test
* update test-vectors due to added `Type` field
* change Type field from string to byte and add new type alias
- SignedMsgType replaces VoteTypePrevote, VoteTypePrecommit and adds new
ProposalType to separate votes from proposal when signed
- update test-vectors
* fix remains from rebasing
* use SignMessageType instead of byte everywhere
* fixes from review
Ismail Khoffi
Zarko Milosevic
Jae Kwon
Ethan Buchman