added lifetime example

Author: BartMassey

README.md

@@ -11,3 +11,4 @@ in a controlled repository now.
 * `strings.rs`: string and str examples
 * `iterators.rs`: iterator examples
 * `closures.rs`: closure examples
+* `lifetimes.rs`: simple lifetime example

lifetimes.rs

@@ -0,0 +1,8 @@
+fn call_me() -> &'static u64 {
+    let y = 5;
+    return &y;
+}
+
+fn main() {
+    println!("{}", call_me());
+}