message: use stderr, exit with failure code
diff: use std::env;
  use std::str::FromStr;
  +use std::process;
  use clap::{App, AppSettings, Arg, SubCommand};
  use commands::HTTPMethod;
  @@ -31,7 +32,8 @@ fn main() {
  {
  installer::install();
  } else if let Err(e) = run() {
  - println!("{}", e);
  + eprintln!("{}", e);
  + process::exit(1);
  }
  }
  }
  