Doc change: add notice for admob sdk upgrade.

</div>

</div>

<div style=

"background-color:#fffdeb;width:100%;margin-bottom:1em;padding:.5em;" class=

"caution">

  <p><strong>Upgrade to the new AdMob</strong></p>

  <p>Legacy AdMob will be shutting down on August 31, 2014. Beginning August 31,

    you will no longer be able to use legacy AdMob to promote and monetize your

    apps. Specifically, please be aware of the following:</p>

  <ol style="margin-bottom:0;">

    <li>Ads will stop serving to legacy ad units that are not updated with new

    ad unit IDs.</li>

    <li>Legacy house ad campaigns will stop serving.</li>

    <li>You will not be able to access the legacy AdMob UI after August 31,

    2014.</li>

  </ol>

  <p>If you are still using legacy AdMob, please upgrade your account to the new

    AdMob as soon as possible. Upgrading takes only 5 minutes. <a href=

    "https://apps.admob.com/admob/signup?">Start here</a>.</p>

</div>

<div class="landing-docs">

  <div class="col-6 normal-links">

    <h3 style="clear:left">Key Developer Features</h3>