Fix debian unstable installation

Treat debian unstable as ubuntu too

Tested on debian unstable
do an elif instead of double if

provide better info message
Merge pull request #12 from vvo/debian-unstable-fix

Fix debian unstable installation
configure: debian wheezy is 7.*, not just 7.0 (#13)
README update
Merge branch 'devel' of github.com:leamas/spotify-make into devel
README: typo