add instructions to use class without Symfony2

[lukeholder]

Could I use this composer module in as a class in a regular composer friendly non symfony app?

[mgallego]

This project is only for Symfony2. Could try to use https://github.com/mgallego/PHPDucksboardApi but is possible may not work properly as it is not maintained. You are free to change what you feel is necessary to use it.

thank you very much