Use dep to vendor things

vendor/github.com/faiface/pixel/pixelgl/run.go

@@ -0,0 +1,33 @@
+package pixelgl
+
+import (
+	"github.com/faiface/mainthread"
+	"github.com/go-gl/glfw/v3.2/glfw"
+	"github.com/pkg/errors"
+)
+
+// Run is essentially the main function of PixelGL. It exists mainly due to the technical
+// limitations of OpenGL and operating systems. In short, all graphics and window manipulating calls
+// must be done from the main thread. Run makes this possible.
+//
+// Call this function from the main function of your application. This is necessary, so that Run
+// runs on the main thread.
+//
+//   func run() {
+//       // interact with Pixel and PixelGL from here (even concurrently)
+//   }
+//
+//   func main() {
+//       pixel.Run(run)
+//   }
+//
+// You can spawn any number of goroutines from your run function and interact with PixelGL
+// concurrently. The only condition is that the Run function is called from your main function.
+func Run(run func()) {
+	err := glfw.Init()
+	if err != nil {
+		panic(errors.Wrap(err, "failed to initialize GLFW"))
+	}
+	defer glfw.Terminate()
+	mainthread.Run(run)
+}