Fix ids setter for Person and TVEpisode

[glensc]

Fix #14

Person and TVSeason _build methods are different, they call ids first before _ids, so therefore we need setter for ids. Unfortunately, that data is not even tested, so this did not come out in any way.

Typically it's like this:

• python-pytrakt/trakt/movies.py

  Lines 125 to 131 in b5dfbeb

  	def _build(self, data):
  	"""Build this :class:`Movie` object with the data in *data*"""
  	for key, val in data.items():
  	if hasattr(self, '_' + key):
  	setattr(self, '_' + key, val)
  	else:
  	setattr(self, key, val)

but Person and TVSeason have:

• python-pytrakt/trakt/people.py

  Lines 64 to 70 in b5dfbeb

  	def _build(self, data):
  	for key, val in data.items():
  	try:
  	setattr(self, key, val)
  	except AttributeError as ae:
  	if not hasattr(self, '_' + key):
  	raise ae

• python-pytrakt/trakt/people.py

  Lines 64 to 70 in b5dfbeb

  	def _build(self, data):
  	for key, val in data.items():
  	try:
  	setattr(self, key, val)
  	except AttributeError as ae:
  	if not hasattr(self, '_' + key):
  	raise ae

[glensc]

Should refactor this and add common class for the _build() method