Refactor `main.rs` to use `if let` construction

src/main.rs

@@ -7,8 +7,7 @@ fn main() {
     let args: Vec<String> = env::args().collect();
     let filename = &args[1];
     let config = unreal_config::load_file(Path::new(filename));
-    match config {
-        Ok(config) => print!("{}", config),
-        _ => (),
+    if let Ok(config) = config {
+        print!("{}", config);
     }
 }