Fixed self-update url

Author: dgil

captain.go

@@ -278,7 +278,7 @@ func SelfUpdate() {
 
 	info("Checking the last version of Captain...")
 	version := findLastVersion()
-	downloadUrl := fmt.Sprintf("https://github.com/harbur/captain/releases/download/%s/captain-%s-%s", version, kernel, arch)
+	downloadUrl := fmt.Sprintf("https://github.com/harbur/captain/releases/download/%s/captain_%s_%s", version, kernel, arch)
 	downloadedVersionPath := filepath.FromSlash(binariesDir + "/captain-" + version)
 
 	if currentVersionPath == downloadedVersionPath {