Update Exercises Directory Names to Reflect Order

exercises/10_modules/modules3.rs

@@ -0,0 +1,21 @@
+// modules3.rs
+//
+// You can use the 'use' keyword to bring module paths from modules from
+// anywhere and especially from the Rust standard library into your scope. Bring
+// SystemTime and UNIX_EPOCH from the std::time module. Bonus style points if
+// you can do it with one line!
+//
+// Execute `rustlings hint modules3` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+// TODO: Complete this use statement
+use ???
+
+fn main() {
+    match SystemTime::now().duration_since(UNIX_EPOCH) {
+        Ok(n) => println!("1970-01-01 00:00:00 UTC was {} seconds ago!", n.as_secs()),
+        Err(_) => panic!("SystemTime before UNIX EPOCH!"),
+    }
+}