Create a task

        :param subject: the task's subject
        :param desc: the task's content in plain-text
        :returns: the task's id

def create_task(self, subject, desc):
        """Create a task

        :param subject: the task's subject
        :param desc: the task's content in plain-text
        :returns: the task's id
        """
        task = zobjects.Task()
        task_creator = task.to_creator(subject, desc)
        resp = self.request('CreateTask', task_creator)
        task_id = resp['calItemId']
        return task_id