Change --host argument to --uri/--url

Also correct startup text terminology. Maintains --host as a hidden alias for the time being.
Fixes #9

Author: Isona

src/arg_parse.rs

@@ -89,7 +89,9 @@ EXAMPLE USE:
                             .display_order(10))
                         .arg(Arg::with_name("extra_hosts")
                             .short("u")
-                            .long("host")
+                            .long("uri")
+                            .visible_alias("url")
+                            .alias("host")
                             .value_name("host_uri")
                             .help("Additional hosts to scan")
                             .takes_value(true)

src/output.rs

@@ -189,7 +189,7 @@ pub fn startup_text(global_opts: Arc<GlobalOpts>) {
     println!("Dirble {}", crate_version!());
     println!("Developed by Izzy Whistlecroft\n");
 
-    println!("Hosts: {}", global_opts.hostnames.clone().join(" "));
+    println!("Targets: {}", global_opts.hostnames.clone().join(" "));
     println!("Wordlists: {}", global_opts.wordlist_files.clone().join(" "));
 
     if global_opts.prefixes.len() == 1 && global_opts.prefixes[0] == "" {