Skeleton for IPN
Merge branch 'develop' into feature/ipn
Work on IPN.
Added configurations specific to ipn.
Added some validations in the controller.
Added a default route to capture ipn requests.
Merge branch 'develop' of https://github.com/Hete/kohana-paypal into feature/ipn
Added support for more apis. (Skeleton only).

Response_PayPal constructor requires the Request_PayPal as first parameter, because errors are dealed internally.
Response_PayPal::check() throws a PayPal_Exception if it does not validate, allowing better builder syntax such as:

$request->
    execute()
    ->rule(<add_some_custom_rules_here>) // Add rules
    ->check() // Recheck with new rules
    ->data(<fetch_a_specific_data>); // Fetch your data

Fixed some bugs and unworking requests.
Worked on IPN stuff.
Tests from an api are stored in a single file vs creating hundreds of files with only one or 2 tests.
Added a PayPal_Validation_Exception.
Updated README with examples and advanced documentation.