* types: add Version to Header
* abci: add Version to Header
* state: add Version to State
* node: check software and state protocol versions match
* update changelog
* docs/spec: update for versions
* state: more tests
* remove TODOs
* remove empty test
Now that Tendermint Amino will be compatible with proto3, the Header in ABCI
should exactly match the Tendermint header - they will then be encoded
identically in ABCI and in Tendermint Core.
Refs #265