updated version in grafana-server main.go

pkg/cmd/grafana-server/main.go

@@ -26,7 +26,7 @@ import (
 	_ "github.com/grafana/grafana/pkg/tsdb/testdata"
 )
 
-var version = "3.1.0"
+var version = "4.0.0"
 var commit = "NA"
 var buildstamp string
 var build_date string