Implement pluralize() about stringy

[danielstjules]

I'd rather keep inflector classes out of stringy, since it'd be quite a lot of work to create one that's multilingual, and many are english-only. For example, both Laravel and its underlying Inflector are english-only:

• https://github.com/laravel/framework/blob/9497c13bb0e22bb43db5ccde56b8354c2169003a/src/Illuminate/Support/Pluralizer.php
• https://github.com/doctrine/inflector/blob/master/lib/Doctrine/Common/Inflector/Inflector.php

Maybe it'd be worth extending Stringy in your project, adding any pluralize/singularize methods to the child class? :)

[hipsterjazzbo]

Had a go, see #170 :)