Fixes white screen of death when tour ids are not in TapConfig.plist

TourTabBarViewController : adding & using a default config for tours in TapConfig.plist which is used when no custom tour config (referenced by id) is available inside TapConfig.plist
Some "little" improvements to the video : added a french alternative audio track, added an english subtitle track, added a french subtitle track.
Corrections.
Merge branch 'i18n' of https://github.com/ideesculture/tap-ios into i18n