Merge #1685: Improve the public API for Feerate and Weight

b0b0cdb Improve the public API for Feerate and Weight (yancy)

Pull request description:

  Small nit for #1627 to re-export `Weight` and `FeeRate` to shorten the use path.

  ```
  use bitcoin::Weight;
  use bitcoin::FeeRate;
  ````

ACKs for top commit:
  tcharding:
    ACK b0b0cdb
  Kixunil:
    ACK b0b0cdb
  apoelstra:
    ACK b0b0cdb

Tree-SHA512: 81e508c980c4f37e3791d26616459608dd60e5a6255ef28b3a049c1d27281b2853b92474d42f10031254c8c46878adf666eb709826aa4ffde1b4b3542451e080

bitcoin/src/lib.rs

@@ -121,9 +121,11 @@ use core2::io;
 pub use crate::address::{Address, AddressType};
 pub use crate::amount::{Amount, Denomination, SignedAmount};
 pub use crate::blockdata::block::{self, Block};
+pub use crate::blockdata::fee_rate::FeeRate;
 pub use crate::blockdata::locktime::{self, absolute, relative};
 pub use crate::blockdata::script::{self, Script, ScriptBuf};
 pub use crate::blockdata::transaction::{self, OutPoint, Sequence, Transaction, TxIn, TxOut};
+pub use crate::blockdata::weight::Weight;
 pub use crate::blockdata::witness::{self, Witness};
 pub use crate::blockdata::{constants, opcodes};
 pub use crate::consensus::encode::VarInt;