Added links for AOT and tree-shaking. (#1159)

Author: Jinjiang

src/v2/guide/comparison.md

@@ -176,7 +176,7 @@ Finally, although not as deeply integrated with TypeScript as Angular is, Vue al
 
 In terms of performance, both frameworks are exceptionally fast and there isn't enough data from real world use cases to make a verdict. However if you are determined to see some numbers, Vue 2.0 seems to be ahead of Angular according to this [3rd party benchmark](http://stefankrause.net/js-frameworks-benchmark4/webdriver-ts/table.html).
 
-Recent versions of Angular, with AOT compilation and tree-shaking, have been able to get its size down considerably. However, a full-featured Vue 2 project with Vuex + Vue Router included (~30KB gzipped) is still significantly lighter than an out-of-the-box, AOT-compiled application generated by `angular-cli` (~130KB gzipped).
+Recent versions of Angular, with [AOT compilation](https://en.wikipedia.org/wiki/Ahead-of-time_compilation) and [tree-shaking](https://en.wikipedia.org/wiki/Tree_shaking), have been able to get its size down considerably. However, a full-featured Vue 2 project with Vuex + Vue Router included (~30KB gzipped) is still significantly lighter than an out-of-the-box, AOT-compiled application generated by `angular-cli` (~130KB gzipped).
 
 ### Flexibility