message: Fix initialization sequence.
  Setting required OpenGL version should be done before opening a window,
  otherwise it has no effect.
diff: @@ -155,14 +155,14 @@ impl GraphicsContext {
  screen_height: u32)
  -> GameResult<GraphicsContext> {
  + let gl = video.gl_attr();
  + gl.set_context_version(GL_MAJOR_VERSION, GL_MINOR_VERSION);
  + gl.set_context_profile(sdl2::video::GLProfile::Core);
  +
  let window_builder = video.window(window_title, screen_width, screen_height);
  let (mut window, mut gl_context, mut device, mut factory, color_view, depth_view) =
  gfx_window_sdl::init(window_builder).unwrap();
  -
  - let gl = video.gl_attr();
  - gl.set_context_version(GL_MAJOR_VERSION, GL_MINOR_VERSION);
  - gl.set_context_profile(sdl2::video::GLProfile::Core);
  println!("Requested GL {}.{} Core profile, actually got GL {}.{} {:?} profile.",
  GL_MAJOR_VERSION,
  GL_MINOR_VERSION,
  