removing form tag from search

This basically reverts !298 (5df5e029)

search.md

@@ -18,11 +18,9 @@ excerpt:
 Type in your keywords.
 Maximum number of results shown is 20.
 
-<form role="search">
-<div id="form-group">
-    <input type="search" id="search-input" placeholder="Search..." class="form-control">
-    <ul id="results-container"></ul>
-</div>
+<input type="search" id="search-input" placeholder="Search..." class="form-control">
+
+<ul id="results-container"></ul>
 
 <script src="{{ base_url }}/js/simple-jekyll-search.js"></script>
 
@@ -38,7 +36,6 @@ Maximum number of results shown is 20.
     exclude: ['Welcome']
     })
 </script>
-</form>
 
 For this search functionality, [Simple Jekyll Search](https://github.com/christian-fei/Simple-Jekyll-Search) is used, which is released under [MIT license](https://github.com/christian-fei/Simple-Jekyll-Search/blob/master/LICENSE.md).