project: use vndr for vendoring

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

vendor/github.com/docker/go-events/event.go

@@ -0,0 +1,15 @@
+package events
+
+// Event marks items that can be sent as events.
+type Event interface{}
+
+// Sink accepts and sends events.
+type Sink interface {
+	// Write an event to the Sink. If no error is returned, the caller will
+	// assume that all events have been committed to the sink. If an error is
+	// received, the caller may retry sending the event.
+	Write(event Event) error
+
+	// Close the sink, possibly waiting for pending events to flush.
+	Close() error
+}