Refactored CpInfo to be more nested

So I can only refer to a single variant

src/main.rs

@@ -1,10 +1,25 @@
-use coldsquare::parse_class_file;
+use coldsquare::{display_class, parse_class_file};
 
 fn main() {
-    let file = "Test.class";
-    let file = std::fs::read(file).unwrap();
+    let file = std::env::args().nth(1).unwrap_or_else(|| {
+        eprintln!("No file provided");
+        std::process::exit(1);
+    });
+    let file = std::fs::read(file).unwrap_or_else(|_| {
+        eprintln!("Could not read file");
+        std::process::exit(1);
+    });
 
-    let class_file = parse_class_file(&file).unwrap();
+    let class_file = match parse_class_file(&file) {
+        Ok(file) => file,
+        Err(err) => {
+            eprintln!("{}", err);
+            return;
+        }
+    };
+    let stdout = std::io::stdout();
 
-    println!("{:?}", class_file);
+    if let Err(why) = display_class(stdout.lock(), &class_file) {
+        eprintln!("{}", why);
+    }
 }