fix perf in IE9

Author: yyx990803

source/perf/index.md

@@ -1,8 +1,6 @@
 title: Performance Comparisons
 ---
 
-# {{title}}
-
 ## TodoMVC Benchmark
 
 This is a benchmark found in the [webkit performance tests](https://github.com/WebKit/webkit/tree/master/PerformanceTests/DoYouEvenBench) based on the [TodoMVC](http://todomvc.com/) project. For each framework implementation, add 100 todos, toggle them one by one, then delete them one by one. In addition to the most popular MV* libraries, I also included [Om](https://github.com/swannodette/om) (a ClojureScript interface on top of React which boasts of performance) and [Ractive](http://www.ractivejs.org/) (very similar in terms of use case and API).

themes/vue/source/js/benchmark.js

@@ -46,7 +46,7 @@
                 i = bars.length
             while (i--) {
                 var bar = bars[i],
-                    t = bar.dataset.time,
+                    t = bar.getAttribute('data-time'),
                     pct = ~~(t / max * 100)
                 if (t == min) bar.className = 'bar min'
                 bar.querySelector('.inner').style.width = pct + '%'