Add web listen address as config variable

bot.go

 	Password            string
 	SpotifyClientID     string
 	SpotifyClientSecret string
+	ListenAddr          string
 }
 
 func appendSong(wikiText string, author string, newSong string) string {
 	spotifyClient := spotify.NewClient(credentials.SpotifyClientID, credentials.SpotifyClientSecret)
 	go func() {
 
-		webStart(modifiedSongChan, spotifyClient)
+		webStart(credentials.ListenAddr, modifiedSongChan, spotifyClient)
 	}()
 
 	go func() {

web.go

 	http.Redirect(w, r, "/", http.StatusTemporaryRedirect)
 }
 
-func webStart(modifiedSongChan chan *SongEntry, spot *spotify.SpotifyClient) {
+func webStart(listenAddr string, modifiedSongChan chan *SongEntry, spot *spotify.SpotifyClient) {
 	songsChan = modifiedSongChan
 	spotifyClient = spot
 
 	mux.HandleFunc("/update", updateHandler)
 	mux.HandleFunc("/login", loginHandler)
 
-	http.ListenAndServe("localhost:8080", mux)
+	http.ListenAndServe(listenAddr, mux)
 }