feat(gorleaser): set version from git tag on build

- make `GoTomatoVersion` a variable and default it to "devel"
- add ldflags to `.goreleaser.yaml` for version tagging
- remove "v" from output of `-version`

cmd/server/main.go

@@ -28,8 +28,8 @@ func Start() {
 
 	// show server and protocl version and exit
 	if *showVersionFlag {
-		fmt.Printf("Server-Version: v%s\n", metadata.GoTomatoVersion)
-		fmt.Printf("Protocol-Version: v%s\n", metadata.ProtocolVersion)
+		fmt.Println("Server-Version:", metadata.GoTomatoVersion)
+		fmt.Println("Protocol-Version:", metadata.ProtocolVersion)
 		os.Exit(0)
 	}