Reworked the PHP OOP Design

I was using the API and I didn' t like the way how it puts all these classes and functions into my global namespace, therefor I re-organized the structure a bit

* Every class exists in it' s own class and has a namespace [PSR-0](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md).
* Moved these ```_utils_ ``` functions into a "static" class.
* Fixed in this new version some bugs, e.g. sending content-type with the request and using ```explode()``` instead of ```split()``` (which is deprecated).

The current version (```chatterbotapi.php```) is still there and can co-exists with the this version perfectly. This (of this pull-request) is just a bit more convient and up-to-date.

The logic it self is **untouched**!!

Cheers,

Christian