Add buttons to copy installation commands

This PR is for adding buttons described in #26:

![screenshot from 2015-01-01 20 51 40](https://cloud.githubusercontent.com/assets/3458255/5593132/10d83292-91f8-11e4-8a84-6daddecb8016.png)

Above is for desktop users (detected using lib from http://detectmobilebrowsers.com/)

Mobile users has commands wrapped in <input> tags which makes them easier to copy manualy.