Setup Travis CI

[Juanito Fatas]

• .travis.yml
• we only need to test Ruby 2.1.x and 2.2.x and ruby-head (but allow it to fail)
• svg badge

[Puff]

Note : Travis CI require admin rights.

[Juanito Fatas]

Note : Travis CI require admin rights.

Enabled. Now you can follow this guide to set it up, thanks!

[Puff]

svg badge paste to README.md

[![Build Status](https://travis-ci.org/rubytaiwan/rubytw-reboot.svg?branch=master)](https://travis-ci.org/rubytaiwan/rubytw-reboot)