Add a Update object to the database
		
		Arguments:
		trainer - expects a int of trainer's id or a trainer object
		xp
		time_updated - expects datetime.datetime

def create_update(self, trainer, xp, time_updated=None):
		"""Add a Update object to the database
		
		Arguments:
		trainer - expects a int of trainer's id or a trainer object
		xp
		time_updated - expects datetime.datetime
		
		"""
		
		if isinstance(trainer, Trainer):
			trainer = trainer.id
		url = api_url+'trainers/'+str(trainer)+'/updates/'
		payload = {'trainer' : int(trainer), 'xp' : int(xp)}
		
		if time_updated is None:
			payload['update_time'] = maya.now().iso8601()
		else:
			payload['update_time'] = time_updated.iso8601()
		if self.identifier:
			payload['meta_source'] = self.identifier
		
		r = requests.post(url, data=json.dumps(payload), headers=self.headers)
		print(request_status(r))
		r.raise_for_status()
		return Update(r.json())