feat: update home page banner to announce v4

Author: IgorMinar

public/_includes/_hero-home.jade

@@ -8,6 +8,6 @@ header(class="background-sky l-relative")
     announcement-bar
       .announcement-bar-slide.clearfix
         img(src="/resources/images/logos/angular2/angular-banner-logo-grey.png" width="64")
-        p Test-drive <strong>@angular/material</strong>: 22 components now in beta.
-        a(href="https://material.angular.io/" target="_blank" class="button md-button") Try now
+        p Angular v4.0 is out! Smaller, faster, no biggie...
+        a(href="http://angularjs.blogspot.com/2017/03/angular-400-now-available.html" target="_blank" class="button md-button") Learn more