Added Butter.app v0.1.2

Butter is a client application for the chat service named "idobata".

harukasan/butter: http://github.com/harukasan/butter
idobata: https://idobata.io

![2014-03-28 10 36 51](https://cloud.githubusercontent.com/assets/264469/2545548/9006ea24-b619-11e3-865a-27366f0c978f.png)