better example program

src/bin/bitsy-validate.rs

@@ -0,0 +1,14 @@
+extern crate bitsy_parser;
+use bitsy_parser::game::Game;
+use bitsy_parser::image::Image;
+use std::{env, fs};
+
+fn main() {
+    let input_file = env::args()
+        .nth(1)
+        .expect("No input path specified. Usage: `smiley infile outfile`");
+
+    Game::from(fs::read_to_string(input_file).unwrap()).unwrap();
+
+    println!("OK!");
+}