add missing vendor file

vendor/github.com/sirupsen/logrus/terminal_check_appengine.go

@@ -0,0 +1,11 @@
+// +build appengine gopherjs
+
+package logrus
+
+import (
+	"io"
+)
+
+func checkIfTerminal(w io.Writer) bool {
+	return true
+}