Disable unused bootstrap components

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/assets/stylesheets/gl_bootstrap.scss

@@ -30,9 +30,7 @@
 @import "bootstrap/thumbnails";
 @import "bootstrap/alerts";
 @import "bootstrap/progress-bars";
-@import "bootstrap/media";
 @import "bootstrap/list-group";
-@import "bootstrap/panels";
 @import "bootstrap/wells";
 @import "bootstrap/close";