Linux apt improvement

[gerb1]

This is a simple suggestion to make the Spotify Linux Client much more robust. I recommend that you include a 'check' in your apt script to check for the existence of /etc/apt/source.list.d/spotify.sources before automatically recreating /etc/apt/sources.list.d/spotify.list - /etc/apt/sources.list.d/spotify.sources is actually a more modern structure and the automatic creation of /etc/apt/sources.list.d/spotify.list creates redundant duplicates when apt runs. Thank You