Feature: Incorporate site search into masthead (#1383)

* Integrate search into masthead
* Fix cutoff descenders in archive article titles
* Remove search page from `/test` site
* Enable masthead search
* Remove dedicated search page
* Fix masthead search form padding
* Improve insertion of search content
* Speed up page transition
* Add fade transition to search content
* Rename visibility class names
* Add `site.search` to _config.yml
* Document site search feature
* Update CHANGELOG and history

docs/_docs/10-layouts.md

@@ -7,7 +7,7 @@ single_layout_gallery:
     alt: "single layout with header example"
   - image_path: /assets/images/mm-layout-single-meta.png
     alt: "single layout with comments and related posts"
-last_modified_at: 2017-11-28T08:42:54-05:00
+last_modified_at: 2017-12-06T14:58:04-05:00
 toc: true
 toc_label: "Included Layouts"
 toc_icon: "columns"
@@ -275,6 +275,9 @@ A page with a search form. Add `layout: search` to the YAML Front Matter similar
 
 ![search page layout example]({{ "/assets/images/search-layout-example.png" | absolute_url }})
 
+**Note:** A page using the `layout: search` isn't compatible with the new [site search feature]({{ "/docs/configuration/#site-search" | absolute_url }}) incorporated in the masthead.
+{: .notice--warning}
+
 ### Exclusions
 
 If you would like to exclude specific pages/posts from the search index set the search flag to `false` in the YAML Front Matter for the page/post.