move dependencies to vendor

vendor/github.com/docker/libcompose/logger/null.go

@@ -0,0 +1,18 @@
+package logger
+
+// NullLogger is a logger.Logger and logger.Factory implementation that does nothing.
+type NullLogger struct {
+}
+
+// Out is a no-op function.
+func (n *NullLogger) Out(_ []byte) {
+}
+
+// Err is a no-op function.
+func (n *NullLogger) Err(_ []byte) {
+}
+
+// Create implements logger.Factory and returns a NullLogger.
+func (n *NullLogger) Create(_ string) Logger {
+	return &NullLogger{}
+}