Add missing close import

static/bootstrap.less

@@ -23,6 +23,7 @@
 @import "../node_modules/bootstrap/less/alerts.less";
 @import "../node_modules/bootstrap/less/list-group.less";
 @import "../node_modules/bootstrap/less/thumbnails.less";
+@import "../node_modules/bootstrap/less/close.less";
 
 // Components w/ JavaScript
 @import "../node_modules/bootstrap/less/tooltip.less";