change how collapse works - collapse, collapsing, and in

dist/css/bootstrap.css

@@ -2016,6 +2016,14 @@ input[type="button"].btn-block {
 }
 
 .collapse {
+  display: none;
+}
+
+.collapse.in {
+  display: block;
+}
+
+.collapsing {
   position: relative;
   height: 0;
   overflow: hidden;
@@ -2023,10 +2031,6 @@ input[type="button"].btn-block {
           transition: height 0.35s ease;
 }
 
-.collapse.in {
-  height: auto;
-}
-
 .caret {
   display: inline-block;
   width: 0;