Support specifying a URL on the command line.

This change will visit the first URL passed in on the command line.

src/main.rs

@@ -67,6 +67,10 @@ fn main() {
         .with_id("container"),
     );
 
+    if args.len() > 1 {
+        goto_url(&mut siv, &args[1]);
+    }
+
     // We can quit by pressing q
     siv.add_global_callback('q', |s| s.quit());
     // pressing g prompt for an URL