support skype4py backend.
fix bug for empty attributes.
bug fix getting users list: guessing it's from an API change in skype
Merge branch 'master' of github.com:gtp/emacs-skype
support old & new api for retrieving friend list
Merge pull request #1 from lateau/master

retrieving friend list
Merge pull request #2 from gtp/master

fix for groups