Update faq re async I/O

Author: brson

en-US/faq.md

@@ -879,7 +879,7 @@ For buffered reads, use the [`BufReader`][BufReader] struct, which helps to redu
 How do I do asynchronous input / output in Rust?
 </a></h3>
 
-There are several libraries providing asynchronous input / output in Rust, including [mioco](https://github.com/dpc/mioco), [coio-rs](https://github.com/zonyitoo/coio-rs), and [rotor](https://github.com/tailhook/rotor).
+There are several libraries providing asynchronous input / output in Rust, including [mio](https://github.com/carllerche/mio), [tokio](https://github.com/tokio-rs/tokio-core), [mioco](https://github.com/dpc/mioco), [coio-rs](https://github.com/zonyitoo/coio-rs), and [rotor](https://github.com/tailhook/rotor).
 
 <h3><a href="#how-do-i-get-command-line-arguments" name="how-do-i-get-command-line-arguments">
 How do I get command line arguments in Rust?