Use dep to vendor things

vendor/github.com/faiface/glhf/interface.go

@@ -0,0 +1,11 @@
+package glhf
+
+// BeginEnder is an interface for manipulating OpenGL state.
+//
+// OpenGL is a state machine. Every object can 'enter' it's state and 'leave' it's state. For
+// example, you can bind a buffer and unbind a buffer, bind a texture and unbind it, use shader
+// and unuse it, and so on.
+type BeginEnder interface {
+	Begin()
+	End()
+}