Merge pull request #10662 from kevinlisota/thumbnail-images

add responsive CSS to hyperlinked images when thumbnail caption markup used

less/thumbnails.less

@@ -14,7 +14,8 @@
   border-radius: @thumbnail-border-radius;
   .transition(all .2s ease-in-out);
 
-  > img {
+  > img,
+  a > img {
     .img-responsive();
     margin-left: auto;
     margin-right: auto;