rustfmt: whoops, let's put a semicolon there

maybe I should have actually looked at what rustfmt produced before I
just blindly accepted it and pushed it onto master.

src/interpret.rs

@@ -275,9 +275,11 @@ impl ExecEnv {
                 // here at some point. ~~Alex
                 exit(random());
             }
-            StmtKind::Rickroll => stdout()
-                .write_all(include_str!("rickroll").as_bytes())
-                .expect("Failed to write to stdout"),
+            StmtKind::Rickroll => {
+                stdout()
+                    .write_all(include_str!("rickroll").as_bytes())
+                    .expect("Failed to write to stdout");
+            }
         }
 
         Ok(HaltStatus::Finished)