Improve configuration with config file

This adds explanations to the example config file, renames the file
in order to enable yaml syntax highlighting and fixes the parsing of
the flag specifying where to find the configuration file.

main.go

@@ -63,7 +63,9 @@ func shutdownOnOSSignal(server *http.Server) {
 }
 
 func main() {
-	config.InitConfig()
+	if err := config.InitConfig(); err != nil {
+		log.WithError(err).Warn("Could not initialize configuration")
+	}
 	logging.InitializeLogging(config.Config.Logger.Level)
 	server := initServer()
 	log.WithField("address", server.Addr).Info("Starting server")