Add usage info to readme
Added contributing informations

It's base on the [Symfony contributing standard][0].

[0]: http://symfony.com/doc/current/contributing/code/patches.html
Improve English in contributor guidelines
Merge pull request #48 from alquerci/add/contributing

Added contributing informations
Merge pull request #13 from nylen/add-usage-info

Add usage info to readme
Added a backward compatibility for `skipTest` method for python 2.6