Vendor dependencies

Let's see how I like this workflow.

vendor/users/examples/switching.rs

@@ -0,0 +1,29 @@
+extern crate users;
+use users::{get_current_uid, get_current_gid, get_effective_uid, get_effective_gid, uid_t};
+use users::switch::switch_user_group;
+use std::mem::drop;
+
+extern crate env_logger;
+
+
+const SAMPLE_ID: uid_t = 502;
+
+fn main() {
+    env_logger::init();
+
+    println!("\nInitial values:");
+    print_state();
+
+    println!("\nValues after switching:");
+    let guard = switch_user_group(SAMPLE_ID, SAMPLE_ID);
+    print_state();
+
+    println!("\nValues after switching back:");
+    drop(guard);
+    print_state();
+}
+
+fn print_state() {
+    println!("Current UID/GID: {}/{}",   get_current_uid(),   get_current_gid());
+    println!("Effective UID/GID: {}/{}", get_effective_uid(), get_effective_gid());
+}