Add support for showing latest dev/stable versions

app/views/pkg/show.mustache

 {{! Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
     for details. All rights reserved. Use of this source code is governed by a
     BSD-style license that can be found in the LICENSE file. }}
 
 <h1>
   {{package.name}}
-  <span class="version">{{package.latest_version.version}}</span>
+  <span class="version">{{package.selected_version.version}}</span>
+  <span class="version" style="font-weight: normal">
+    {{#package.latest.should_show}}
+    (latest:

[Søren Gjesse, 2016/06/17 07:03:37]

I saw that you already deployed this, and maybe the "(latest: v1 / v2)" UI could
be more clear, but that can always be changed in the template if someone can
come up with something better.

Do you have some feedback from the requester?

[kustermann, 2016/06/28 09:53:31]

I couldn't get any feedback without deploying and so far didn't get any. But we
can always tweak it if necessary.

The good thing is the UI only changes for packages where there is a newer
pre-release version than the latest stable version (99% of packages don't have
that).

+      <a href="/packages/{{package.name}}/versions/{{package.latest.stable}}" >{{package.latest.stable}}</a>
+    {{#package.latest.should_show_dev}}
+     /
+      <a href="/packages/{{package.name}}/versions/{{package.latest.dev}}" >{{package.latest.dev}}</a>
+    {{/package.latest.should_show_dev}}
+    )
+    {{/package.latest.should_show}}
+  </span>
 </h1>
 <div class="row-fluid">
   <div class="span8">
     <ul class="nav nav-tabs">
       {{#readme}}
         <li class="active">
           <a href="#readme" data-toggle="tab">{{readme_filename}}</a>
         </li>
       {{/readme}}
       {{#changelog}}
@@ skipping 109 matching lines @@
     {{/package.crossdart}}
 
     <h4>{{package.uploaders_title}}</h4>
     <p>{{& package.uploaders_html}}</p>
 
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   </div>
 </div>