message: add transaction list command
diff: @@ -25,7 +25,22 @@ pub fn list( mut term: Term
  , root_dir: PathBuf
  )
  {
  - unimplemented!()
  + let transactions_dir = core::config::transaction_directory(root_dir.clone());
  +
  + for entry in ::std::fs::read_dir(transactions_dir).unwrap() {
  + let entry = entry.unwrap();
  + if entry.file_type().unwrap().is_dir() {
  + term.warn(&format!("unexpected directory in transaction directory: {:?}", entry.path())).unwrap();
  + continue;
  + }
  + let name = entry.file_name().into_string().unwrap_or_else(|err| {
  + panic!("invalid utf8... {:?}", err)
  + });
  +
  + let staging = load_staging(&mut term, root_dir.clone(), name.as_str());
  +
  + writeln!(term, "{}", style!(staging.id())).unwrap();
  + }
  }
  pub fn destroy( mut term: Term
  