Show tag info in the center in MD theme

boards/static/css/md/base_page.css

@@ -115,6 +115,10 body {
     visibility: hidden;
 }
 
+.tag_info {
+    text-align: center;
+}
+
 .header {
     border-bottom: solid 2px #ccc;
     margin-bottom: 5px;