Re-export Witness at crate level. Closes #770

Author: dr-orlovsky

src/lib.rs

@@ -124,6 +124,7 @@ pub use blockdata::transaction::TxIn;
 pub use blockdata::transaction::TxOut;
 pub use blockdata::transaction::OutPoint;
 pub use blockdata::transaction::EcdsaSigHashType;
+pub use blockdata::witness::Witness;
 pub use consensus::encode::VarInt;
 pub use network::constants::Network;
 pub use util::Error;