Highlight affected slices for filter change in dashboard view (#1439)

* Highlight affected slices for filter change in dashboard view
Done:
 - When user adds/deletes a filter in dashboard, affected slices will
   have their header highlighted for 2 seconds

* Modified highlight to a more subtle box shadow

* Added slice-cell class for highlight transition

* Changed class name to slice-cell-highlight

caravel/assets/javascripts/dashboard/components/SliceCell.js

@@ -8,7 +8,7 @@ const propTypes = {
 
 function SliceCell({ expandedSlices, removeSlice, slice }) {
   return (
-    <div>
+    <div className="slice-cell" id={`${slice.token}-cell`}>
       <div className="chart-header">
         <div className="row">
           <div className="col-md-12 header">