Improve error checking paths during startup

[Lekensteyn]

In src/main.rs, there are some code paths that ignore errors. Among the possibly problematic ones are:

• When run as root, any failure to change user/group IDs will not result in a fatal error. This might might increase the risk of running with unnecessary privileged. (btw, the option name is misspelled, fixed small errors #43 was incomplete.)

    if !matches.is_present("disable-drop-priviliges") {
        drop_privileges().ok();
    }

• When running backgrounded (without --foreground), any errors will result in the application being foregrounded anyway. This may be contrary to user expectations.

        match daemonize.start() {
            Ok(_) => println!("Success, daemonized"),
            Err(e) => eprintln!("Error, {}", e),
        }