v2 extended header size calculated corectly for v.2.3.0
private and involved people list frames
Version bump to 0.5.0
Regenerate gemspec for version 0.5.0
Merge remote-tracking branch 'krists/master' into fallback_encode

* krists/master:
  Regenerate gemspec for version 0.5.0
  Version bump to 0.5.0
  private and involved people list frames
  v2 extended header size calculated corectly for v.2.3.0

Conflicts:
	lib/id3tag/frames/v2/comments_frame.rb
	lib/id3tag/frames/v2/text_frame.rb