Updated APNService to send notifications in chunks
Made BaseService connect and disconnect private methods
Removed unnecessary assert from test_pushing_notification_in_chunks
Removed default value for chunk_size from APNService._write_message
Disconnect from FeedbackService in finally clause
Readded accidentally removed comment
Updated documentation
Moved subprocess command in tests to class setup and teardown
Fixed method call to self._write_message
Removed time.sleep from tests setup
Added ability to conrol chunk size from management command
Added validation step to ensure chunk_size is an integer greater than zero
Ensured that either message or extra are provided in push_ios_notification management command
Added test to ensure push_ios_notification command raises an exception when message and extra are not supplied