bitcoin-bech32 0.6.0

# Bitcoin Bech32

Encodes and decodes Bitcoin Segregated Witness addresses in the Bech32 format described in [BIP-0173](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki).

## Example

```rust
use bitcoin_bech32::{WitnessProgram, u5};
use bitcoin_bech32::constants::Network;

let witness_program = WitnessProgram {
     version: u5::try_from_u8(0).unwrap(),
     program: vec![
                 0x00, 0x00, 0x00, 0xc4, 0xa5, 0xca, 0xd4, 0x62, 
                 0x21, 0xb2, 0xa1, 0x87, 0x90, 0x5e, 0x52, 0x66, 
                 0x36, 0x2b, 0x99, 0xd5, 0xe9, 0x1c, 0x6c, 0xe2, 
                 0x4d, 0x16, 0x5d, 0xab, 0x93, 0xe8, 0x64, 0x33],
     network: Network::Testnet
};
 
let address = witness_program.to_address().unwrap();
assert_eq!(address, 
    "tb1qqqqqp399et2xygdj5xreqhjjvcmzhxw4aywxecjdzew6hylgvsesrxh6hy".to_string());

let decoded = WitnessProgram::from_address(address).unwrap();
assert_eq!(decoded, witness_program);
```