Fail on missing closing brackets

src/main.rs

@@ -28,6 +28,10 @@ fn check_brainfuck(prog: &str) -> bool {
             },
         }
     }
+    if brackets > 0 {
+        println!("Not all brackets have been closed, {} remain open", brackets);
+        borked = true;
+    }
     return ! borked;
 }