Updated chefspecs + provider bugfix (Fixes #519)

There were 3 bugs fixed in this commit (one of them was introduced by
me in my refactor):

1.  node attribute `admin_groups' was being checked instead of `groups'
    in find_dsh_group_members()
2.  the node attribute branch for the dsh group was being overwritten
    in configure_pubkey()
3.  the $HOME/.dsh and $HOME/.dsh/group directories were being created
    with root ownership (instead of `user_admin' attribute value)

removed create_dsh_information() because everything about it was wrong.

corrected the chefspec examples (including a stub) to expect different
values, which correspond with the newly-refactored code.