message: Remove unwrap() from library examples
diff: //! ```
  //! use std::io::{Read, Write};
  //!
  +//! # fn run_main() -> std::io::Result<()> {
  //! let key = age::SecretKey::generate();
  //! let pubkey = key.to_public();
  //!
  //! let encryptor = age::Encryptor::Keys(vec![pubkey]);
  //! let mut encrypted = vec![];
  //! {
  -//! let mut writer = encryptor.wrap_output(&mut encrypted).unwrap();
  -//! writer.write_all(plaintext).unwrap();
  -//! writer.flush().unwrap();
  +//! let mut writer = encryptor.wrap_output(&mut encrypted)?;
  +//! writer.write_all(plaintext)?;
  +//! writer.flush()?;
  //! };
  //!
  //! let decryptor = age::Decryptor::Keys(vec![key]);
  -//! let mut reader = decryptor.trial_decrypt(&encrypted[..]).unwrap();
  +//! let mut reader = decryptor.trial_decrypt(&encrypted[..])?;
  //! let mut decrypted = vec![];
  //! reader.read_to_end(&mut decrypted);
  //!
  //! assert_eq!(decrypted, plaintext);
  +//! # Ok(())
  +//! # }
  +//! # fn main() { run_main().unwrap(); }
  //! ```
  //!
  //! ## Passphrase-based encryption
  //! ```
  //! use std::io::{Read, Write};
  //!
  +//! # fn run_main() -> std::io::Result<()> {
  //! let plaintext = b"Hello world!";
  //! let passphrase = "this is not a good passphrase";
  //!
  //! let encryptor = age::Encryptor::Passphrase(passphrase.to_owned());
  //! let mut encrypted = vec![];
  //! {
  -//! let mut writer = encryptor.wrap_output(&mut encrypted).unwrap();
  -//! writer.write_all(plaintext).unwrap();
  -//! writer.flush().unwrap();
  +//! let mut writer = encryptor.wrap_output(&mut encrypted)?;
  +//! writer.write_all(plaintext)?;
  +//! writer.flush()?;
  //! };
  //!
  //! let decryptor = age::Decryptor::Passphrase(passphrase.to_owned());
  -//! let mut reader = decryptor.trial_decrypt(&encrypted[..]).unwrap();
  +//! let mut reader = decryptor.trial_decrypt(&encrypted[..])?;
  //! let mut decrypted = vec![];
  //! reader.read_to_end(&mut decrypted);
  //!
  //! assert_eq!(decrypted, plaintext);
  +//! # Ok(())
  +//! # }
  +//! # fn main() { run_main().unwrap(); }
  //! ```
  // Catch documentation errors caused by code changes.
  