Add a media query style for mobile device so the email doesn't generate
a horizontal bar. Gmail strips out all style, that means we can't apply
the mobile style to Gmail. Luckily, Gmail on mobile device browser
automatically fit into the entire mobile screen
bug: 53057
Change-Id: Ia4350669db2e81ee44d5b53d7cece6fcd8839e7a
To test the HTML email:
1. install the latest version of php-mail and php-mail-mime package, they are required
by the core sendmail function to send HTML email
2. set $wgAllowHTMLEmail = true before loading Echo in LocalSetting.php
Change-Id: Ia4b98b14e135742b84f1b0e04589b0efdd24e954
