rollup merge of #20693: EchoAce/intro-oboe

Issue #20686, proposed by nstoddard.

Author: alexcrichton

src/doc/intro.md

@@ -542,7 +542,7 @@ use std::thread::Thread;
 fn main() {
     let vec = vec![1i, 2, 3];
 
-    for i in range(1u, 3) {
+    for i in range(0u, 3) {
         Thread::spawn(move || {
             println!("{}", vec[i]);
         }).detach();
@@ -558,7 +558,7 @@ a vector:
 ```{rust}
 let vec = vec![1i, 2, 3];
 
-for i in range(1u, vec.len()) {
+for i in range(0u, vec.len()) {
      println!("{}", vec[i]);
 }
 ```