message: Make the message module public
diff: @@ -6,7 +6,7 @@ use chain_core::property::{self, Serialize};
  use chain_crypto::Verification;
  mod header;
  -mod message;
  +pub mod message;
  pub use self::header::{
  BftProof, BftSignature, BlockContentHash, BlockContentSize, BlockId, BlockVersion, Common,
  