Added style for 404 and other error pages

lms/static/sass/_error-pages.scss

+section.outside-app {
+  @extend .container;
+  text-align: left;
+  padding: 80px 0;
+
+  h1 {
+    @extend h2;
+    margin-bottom: 40px;
+  }
+  
+  p {
+    max-width: 600px;
+    margin: 0 auto;
+  }
+}

lms/static/sass/application.scss

@@ -33,6 +33,7 @@
 @import 'about_pages';
 @import 'press_release';
 @import 'password_reset';
+@import 'error-pages';
 
 
 // Courseware styles