(docs) add build badge

Author: antoine92190

.travis.yml

@@ -1,3 +1,5 @@
 language: node_js
 node_js:
   - '8'
+after_success:
+  - bash <(curl -s https://codecov.io/bash)

README.md

@@ -1,8 +1,9 @@
 <p align="center">
-  <a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/dm/vue-advanced-chat.svg"></a>
-  <a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/bundlephobia/minzip/vue-advanced-chat"></a>
-  <a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/v/vue-advanced-chat.svg"></a>
-  <a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/l/vue-advanced-chat.svg"></a>
+<a href="https://travis-ci.org/antoine92190/vue-advanced-chat"><img src="https://img.shields.io/travis/antoine92190/vue-advanced-chat/master.svg"></a>
+<a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/dm/vue-advanced-chat.svg"></a>
+<a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/bundlephobia/minzip/vue-advanced-chat"></a>
+<a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/v/vue-advanced-chat.svg"></a>
+<a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/l/vue-advanced-chat.svg"></a>
 </p>
 
 # vue-advanced-chat