changes: Add 'Changes' section to track changes since previous versions of the spec

This commit also includes updated HTML CSS.

Change-Id: I0f45e3fba25587f97cbb63332d457baacb515f40
diff --git a/named_data_theme/static/default.css_t b/named_data_theme/static/default.css_t
index 5e27530..b582768 100644
--- a/named_data_theme/static/default.css_t
+++ b/named_data_theme/static/default.css_t
@@ -8,7 +8,7 @@
     border: 2px solid #C6C9CB;
     font-size: 1.1em;
     /* margin: 1.5em 0 1.5em 0; */
-    margin: 0;    
+    margin: 0;
     border-right-style: none;
     border-left-style: none;
 }