Improved subclassing of IASKAppSettingsViewController

by not removing all notification observers but just the ones we added
Merge branch 'master' of https://github.com/futuretap/InAppSettingsKit

# By Ortwin Gentz
# Via Ortwin Gentz
* 'master' of https://github.com/futuretap/InAppSettingsKit:
  Improved subclassing of IASKAppSettingsViewController