Ship 'multi-version support'

Closes #25.

assets/javascripts/news.json

@@ -1,5 +1,8 @@
 [
   [
+    "2016-01-24",
+    "&ldquo;Multi-version support&rdquo; has landed!\nClick <a href=\"#\" data-pick-docs>Select documentation</a> to pick which versions to use. More versions will be added in the coming weeks.\nIf you notice any bugs, please report them on <a href=\"https://github.com/Thibaut/devdocs/issues\" target=\"_blank\">GitHub</a>."
+  ], [
     "2015-11-22",
     "New documentations: <a href=\"/phoenix/\">Phoenix</a>, <a href=\"/dojo/\">Dojo</a>, <a href=\"/relay/\">Relay</a> and <a href=\"/flow/\">Flow</a>"
   ], [

assets/javascripts/templates/pages/offline_tmpl.coffee

@@ -29,8 +29,7 @@ app.templates.offlinePage = (docs) -> """
     <dt>Can I close the tab/browser?
     <dd>#{canICloseTheTab()}
     <dt>What if I don't update a documentation?
-    <dd>You'll see outdated content and some pages will be missing or broken, since the rest of the app (including data for the search and sidebar) uses a different caching mechanism which is updated automatically.<br>
-        Documentation versioning is planned for the future but not yet supported, sorry.
+    <dd>You'll see outdated content and some pages will be missing or broken, since the rest of the app (including data for the search and sidebar) uses a different caching mechanism which is updated automatically.
     <dt>I found a bug, where do I report it?
     <dd>In the <a href="https://github.com/Thibaut/devdocs/issues">issue tracker</a>. Thanks!
     <dt>How do I uninstall/reset the app?