message: doc: use HTTPS for LazyloadImagesBlankUrl
  Fixes
diff: @@ -75,9 +75,9 @@ possible to use the same image served by Google's network, or any image that you
  choose, by specifying:</p>
  <dl>
  <dt>Apache:<dd><pre class="prettyprint"
  - >ModPagespeedLazyloadImagesBlankUrl "http://www.gstatic.com/psa/static/1.gif"</pre>
  + >ModPagespeedLazyloadImagesBlankUrl "https://www.gstatic.com/psa/static/1.gif"</pre>
  <dt>Nginx:<dd><pre class="prettyprint"
  - >pagespeed LazyloadImagesBlankUrl "http://www.gstatic.com/psa/static/1.gif";</pre>
  + >pagespeed LazyloadImagesBlankUrl "https://www.gstatic.com/psa/static/1.gif";</pre>
  </dl>
  <p>An advantage of this approach is that this gif may already be in
  the browser cache since any PageSpeed-enabled site can share it.
  