Begin to add missing Resquest classes.
Begin to add missing Response classes.
Update the README.md file with a Contributing section.
Add methods to manage the `data` field in the `Notification` class.
Add methods to manage the `devices` field in the `Notification` class.
Update the Notification class.
Merge branch 'master' of https://github.com/gomoob/php-pushwoosh.git

Conflicts:
	Gruntfile.js
	README.md
	src/main/php/Gomoob/Pushwoosh/Model/Notification/Notification.php
	src/main/php/Gomoob/Pushwoosh/Model/Request/DeleteMessageRequest.php
	src/main/php/Gomoob/Pushwoosh/Model/Request/GetNearestZoneRequest.php
	src/main/php/Gomoob/Pushwoosh/Model/Request/PushStatRequest.php
	src/main/php/Gomoob/Pushwoosh/Model/Request/SetTagsRequest.php
	src/main/php/Gomoob/Pushwoosh/Model/Response/CreateMessageResponse.php
	src/main/php/Gomoob/Pushwoosh/Model/Response/DeleteMessageResponse.php
	src/main/php/Gomoob/Pushwoosh/Model/Response/GetNearestZoneResponse.php
	src/main/php/Gomoob/Pushwoosh/Model/Response/PushStatResponse.php
	src/main/php/Gomoob/Pushwoosh/Model/Response/SetTagsResponse.php