Add usage

README.md

@@ -1,6 +1,6 @@
 # thread-sleep
 
-A native module for when you just need node to back off for a few milliseconds
+A native module for when you just need node to back off for a few milliseconds.  It effectively pauses the current thread.  It may be woken early if an interupt is fired, so it should work pretty well for busy waiting scenarios where you want to check something every few hunderd milliseconds.
 
 [![Linux and Mac Build Status](https://img.shields.io/travis/ForbesLindesay/thread-sleep/master.svg?label=Linux%20%26%20Mac%20Build)](https://travis-ci.org/ForbesLindesay/thread-sleep)
 [![Windows Build Status](https://img.shields.io/appveyor/ci/ForbesLindesay/thread-sleep/master.svg?label=Windows%20Build)](https://ci.appveyor.com/project/ForbesLindesay/thread-sleep)
@@ -11,6 +11,19 @@ A native module for when you just need node to back off for a few milliseconds
 
     npm install thread-sleep
 
+## Usage
+
+```js
+var sleep = require('thread-sleep');
+
+var start = Date.now();
+var res = sleep(1000);
+var end = Date.now();
+// res is the actual time that we slept for
+console.log(res + ' ~= ' + (end - start) + ' ~= 1000');
+// tested on osx and resulted in => 1005 ~= 1010 ~= 1000
+```
+
 ## License
 
   MIT