doc: fix tables

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5676084

doc/go1.html

@@ -7,6 +7,12 @@
 -->
 
 
+<!-- Center the tables, and disable the 1995 3D borders -->
+<style>
+table { margin-left: auto; margin-right: auto; border-style: none; }
+hr { border-style: none; border-top: 1px solid black; }
+</style>
+
 <h2 id="introduction">Introduction to Go 1</h2>
 
 <p>

doc/go1.tmpl

@@ -3,6 +3,12 @@
 }-->
 {{donotedit}}
 
+<!-- Center the tables, and disable the 1995-era 3D borders -->
+<style>
+table { margin-left: auto; margin-right: auto; border-style: none; }
+hr { border-style: none; border-top: 1px solid black; }
+</style>
+
 <h2 id="introduction">Introduction to Go 1</h2>
 
 <p>