[CS2] Async/await documentation; fix for Underscore templating

Cakefile

@@ -184,10 +184,10 @@ task 'doc:site', 'watch and continually rebuild the documentation for the websit
 
   do renderIndex = ->
     codeSnippetCounter = 0
-    rendered = _.template fs.readFileSync(source, 'utf-8'),
+    render = _.template fs.readFileSync(source, 'utf-8')
+    fs.writeFileSync 'index.html', render
       codeFor: codeFor()
       releaseHeader: releaseHeader
-    fs.writeFileSync 'index.html', rendered
     log "compiled", green, "#{source}"
 
   fs.watchFile source, interval: 200, renderIndex

documentation/coffee/async.coffee

@@ -0,0 +1,15 @@
+sleep = (ms) ->
+  new Promise (resolve) ->
+    window.setTimeout resolve, ms
+
+say = (text) ->
+  window.speechSynthesis.cancel() # cancel any prior utterances
+  window.speechSynthesis.speak new SpeechSynthesisUtterance text
+
+countdown = (seconds) ->
+  for i in [seconds..1]
+    say "#{i}"
+    await sleep 1000 # wait one second
+  say "Blastoff!"
+
+countdown(3)

documentation/index.html.js

@@ -829,7 +829,7 @@ Block
 
     <p>
       <span id="fat-arrow" class="bookmark"></span>
-      <b class="header">Bound Functions, Generator Functions</b>
+      <b class="header">Function Modifiers</b>
       In JavaScript, the <code>this</code> keyword is dynamically scoped to mean the
       object that the current function is attached to. If you pass a function as
       a callback or attach it to a different object, the original value of <code>this</code>
@@ -857,17 +857,23 @@ Block
       constructed.
     </p>
     <p>
-      CoffeeScript functions also support
-      <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function*">ES6 generator functions</a>
-      through the <code>yield</code> keyword. There's no <code>function*(){}</code>
-      nonsense &mdash; a generator in CoffeeScript is simply a function that yields.
+      CoffeeScript also supports
+      <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function*">generator functions</a> and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function">async functions</a>
+      through the <code>yield</code> and <code>await</code> keywords respectively. There's no <code>function*(){}</code> or <code>async function(){}</code>
+      nonsense &mdash; a generator in CoffeeScript is simply a function that yields, and an async function in CoffeeScript is simply a function that awaits.
     </p>
     <%= codeFor('generators', 'ps.next().value') %>
     <p>
       <code>yield*</code> is called <code>yield from</code>, and <code>yield return</code>
       may be used if you need to force a generator that doesn't yield.
     </p>
 
+    <%= codeFor('async', true) %>
+    <p>
+      Similar to how <code>yield return</code> forces a generator, <code>await return</code>
+      may be used to force a function to be async.
+    </p>
+
     <p>
       <span id="embedded" class="bookmark"></span>
       <b class="header">Embedded JavaScript</b>