cleanup accordion css and add comments

lib/accordion.less

@@ -1,10 +1,13 @@
 // ACCORDION
 // ---------
 
+
+// Parent container
 .accordion {
   margin-bottom: @baseLineHeight;
 }
 
+// Group == heading + body
 .accordion-group {
   background-color: #f5f5f5;
   .border-radius(4px);
@@ -13,16 +16,12 @@
   padding: 8px 15px;
   border-bottom: 0;
 }
-
 .accordion-body {
-  margin: 0 0 2px;
+  margin-bottom: 2px;
 }
 
+// Inner needs the styles because you can't animate properly with any styles on the element
 .accordion-inner {
   padding: 9px 15px;
   border-top: 1px solid #e5e5e5;
 }
-
-.accordion .in {
-  margin-bottom: @baseLineHeight / 2;
-}