Add a quick_main! variant

[jonasbb]

See quick_main! in error-chain.

1. Print errors:

fn main() {
    use std::io::{self, Write};

    if let Err(err) = run() {
        let stderr = io::stderr();
        let mut out = stderr.lock();
        // cannot handle a write error here, we are already in the outermost layer
        let _ = writeln!(out, "An error occured:");
        for fail in err.iter_chain() {
            let _ = writeln!(out, "  {}", fail);
        }
        let _ = writeln!(out, "{}", err.backtrace());
        std::process::exit(1);
    }
}

2. Setup libraries
   • env_logger: Either generic or custom:

   let log_settings = "client=debug,tlsproxy=debug";
   env_logger::Builder::from_env(env_logger::Env::default().default_filter_or(log_settings))
       .default_format_timestamp_nanos(true)
       .init();

   • https://github.com/athre0z/color-backtrace
   • Maybe structopt