Update Exercises Directory Names to Reflect Order

exercises/10_modules/README.md

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+# Modules
+
+In this section we'll give you an introduction to Rust's module system.
+
+## Further information
+
+- [The Module System](https://doc.rust-lang.org/book/ch07-00-managing-growing-projects-with-packages-crates-and-modules.html)

exercises/10_modules/modules1.rs

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+// modules1.rs
+//
+// Execute `rustlings hint modules1` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+mod sausage_factory {
+    // Don't let anybody outside of this module see this!
+    fn get_secret_recipe() -> String {
+        String::from("Ginger")
+    }
+
+    fn make_sausage() {
+        get_secret_recipe();
+        println!("sausage!");
+    }
+}
+
+fn main() {
+    sausage_factory::make_sausage();
+}

exercises/10_modules/modules2.rs

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+// modules2.rs
+//
+// You can bring module paths into scopes and provide new names for them with
+// the 'use' and 'as' keywords. Fix these 'use' statements to make the code
+// compile.
+//
+// Execute `rustlings hint modules2` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+mod delicious_snacks {
+    // TODO: Fix these use statements
+    use self::fruits::PEAR as ???
+    use self::veggies::CUCUMBER as ???
+
+    mod fruits {
+        pub const PEAR: &'static str = "Pear";
+        pub const APPLE: &'static str = "Apple";
+    }
+
+    mod veggies {
+        pub const CUCUMBER: &'static str = "Cucumber";
+        pub const CARROT: &'static str = "Carrot";
+    }
+}
+
+fn main() {
+    println!(
+        "favorite snacks: {} and {}",
+        delicious_snacks::fruit,
+        delicious_snacks::veggie
+    );
+}

exercises/10_modules/modules3.rs

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+// 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!"),
+    }
+}