Update Travis config

Author: alfredxing

.travis.yml

@@ -0,0 +1,8 @@
+language: ruby
+install:
+- bundle install --jobs=3
+rvm:
+- 2.1
+- 2.0
+- 1.9.3
+script: script/cibuild

README.md

@@ -3,6 +3,7 @@
 Automatically generate post archives by dates, tags, and categories.
 
 [![Gem Version](https://badge.fury.io/rb/jekyll-archives.png)](http://badge.fury.io/rb/jekyll-archives)
+[![Build Status](https://travis-ci.org/jekyll/jekyll-archives.svg?branch=master)](https://travis-ci.org/jekyll/jekyll-archives)
 
 ## Usage