Benchmark: Make results table fixed-width, center everything

benchmark/index.html

@@ -11,9 +11,9 @@
         color: black; background-color: white;
       }
 
-      h1 { margin: 0 0 .75em 0; font-size: 200%; }
+      h1 { margin: 0 0 .75em 0; text-align: center; font-size: 200%; }
 
-      table { border-spacing: 0; border-collapse: collapse; }
+      table { width: 48em; margin: 0 auto; border-spacing: 0; border-collapse: collapse; }
       table td, table th { border: 1px solid silver; padding: .25em 1em; }
       table td .unit { font-size: 75%; color: gray; }
       table td.input-size  { text-align: right; }