Moved away from deprecated thread::sleep_ms

Refactored to use thread::sleep and time::Duration and updated link in
README.md

threads/threads1.rs

@@ -6,6 +6,7 @@
 
 use std::sync::Arc;
 use std::thread;
+use std::time::Duration;
 
 struct JobStatus {
     jobs_completed: u32,
@@ -16,13 +17,13 @@ fn main() {
     let status_shared = status.clone();
     thread::spawn(move || {
         for _ in 0..10 {
-            thread::sleep_ms(250);
+            thread::sleep(Duration::from_millis(250));
             status_shared.jobs_completed += 1;
         }
     });
     while status.jobs_completed < 10 {
         println!("waiting... ");
-        thread::sleep_ms(500);
+        thread::sleep(Duration::from_millis(500));
     }
 }