Made the format links mimic rss/atom feeds

The most common format links are rss/atom feeds, they
are usually white text on red/orange background.

But it wouldn't fit the general color theme or it would
confuse users, so what i suggest is white on light blue
background - but we also include a small 3d effect ;)

Change-Id: I3a9b81b40323626c43af8ca69fd10be3ce143acb

gitiles-servlet/src/main/resources/com/google/gitiles/static/gitiles.css

diff --git a/gitiles-servlet/src/main/resources/com/google/gitiles/static/gitiles.css b/gitiles-servlet/src/main/resources/com/google/gitiles/static/gitiles.css
index b09f027..94460ab 100644
--- a/gitiles-servlet/src/main/resources/com/google/gitiles/static/gitiles.css
+++ b/gitiles-servlet/src/main/resources/com/google/gitiles/static/gitiles.css
@@ -93,6 +93,13 @@
 .formats a {
   font-weight: bold;
   font-size: 70%;
+  color: white;
+  padding: 2px;
+  background-color: #A0ADCC;
+  border-top: #C0CFEE solid 1px;
+  border-left: #C0CFEE solid 1px;
+  border-right: #808A99 solid 1px;
+  border-bottom: #808A99 solid 1px;
 }
 
 .footer {