Bump Pattern Library to v3.0.0

This version of the pattern library includes a breaking change, to
update the markup used for the site header branding icon.

Author: spaceninja

static/css/main.min.css

@@ -85,7 +85,7 @@
             <header class="site-header">
                 <div class="site-branding">
                     <a href="/"><img class="site-branding--logo" src="{{ static_url("images/logo-compact.svg") }}" alt="MLTSHP">
-                    <span class="site-branding--icon" /></a>
+                    <div class="site-branding--icon" aria-label="MLTSHP"></div></a>
                 </div>
                 <nav id="site-nav" class="site-nav">
                     {% block notification_button %}{% end %}