Update jumbotron

* Defaults to no rounded corners and full width in the viewport
* When in a container, the jumbotron has extra padding and will have
rounded corners
* Updates default jumbotron example to show the full width default
display

Fixes #9759.

examples/jumbotron/index.html

@@ -59,15 +59,16 @@
       </div>
     </div>
 
-    <div class="container">
-
-      <!-- Main jumbotron for a primary marketing message or call to action -->
-      <div class="jumbotron">
+    <!-- Main jumbotron for a primary marketing message or call to action -->
+    <div class="jumbotron">
+      <div class="container">
         <h1>Hello, world!</h1>
         <p>This is a template for a simple marketing or informational website. It includes a large callout called the hero unit and three supporting pieces of content. Use it as a starting point to create something more unique.</p>
         <p><a class="btn btn-primary btn-lg">Learn more &raquo;</a></p>
       </div>
+    </div>
 
+    <div class="container">
       <div class="body-content">
 
         <!-- Example row of columns -->

examples/jumbotron/jumbotron.css

@@ -13,10 +13,6 @@ body {
 
 /* Responsive: Portrait tablets and up */
 @media screen and (min-width: 768px) {
-  /* Let the jumbotron breathe */
-  .jumbotron {
-    margin-top: 20px;
-  }
   /* Remove padding from wrapping element since we kick in the grid classes here */
   .body-content {
     padding: 0;