Add capitalize and decapitalize functions

This pull request add ```capitalize``` and ```decapitalize``` functions required on #5 .

![captura de tela 2014-09-18 as 17 49 17](https://cloud.githubusercontent.com/assets/5131269/4323601/d7d4a802-3f51-11e4-814a-a12b5eb1d9c9.png)