Add sdl2 handlers and bunch of tests

First semi-working state, games can be loaded and they open
a sdl2 window \o/

TODOS:
+ Stacks offset is wrong somewhere
+ Input not working (maybe because of above reason?)
+ Add mising tests

src/display.rs

@@ -0,0 +1,52 @@
+use sdl2;
+use sdl2::{render::Canvas, video::Window, pixels, rect::Rect};
+
+pub struct Display {
+    canvas: Canvas<Window>,
+}
+
+impl Display {
+    pub fn new(sdl_ctx: &sdl2::Sdl) -> Self {
+	let video = sdl_ctx.video().unwrap();
+	let window = video
+	    .window(
+		"FooBar",
+		(crate::SCREEN_WIDTH * crate::SCREEN_SCALE) as u32,
+		(crate::SCREEN_HEIGHT * crate::SCREEN_SCALE) as u32)
+            .position_centered()
+            .opengl()
+            .build()
+            .unwrap();
+
+	let mut canvas = window
+	    .into_canvas()
+	    .build()
+	    .unwrap();
+
+	canvas.set_draw_color(pixels::Color::RGB(0, 0, 0));
+	canvas.clear();
+	canvas.present();
+
+	Display {
+	    canvas,
+	}
+    }   
+
+    pub fn draw(&mut self, pixel: &[[u8; crate::SCREEN_WIDTH]; crate::SCREEN_HEIGHT]) {
+	for (y, &row) in pixel.iter().enumerate() {
+	    for (x, &column) in row.iter().enumerate() {
+		self.canvas.set_draw_color(
+		    if column == 1 {
+			pixels::Color::RGB(255, 255, 255)
+		    }
+		    else {
+			pixels::Color::RGB(0, 0, 0)
+		    });
+		let _ = self.canvas
+		    .fill_rect(
+			Rect::new((x * crate::SCREEN_SCALE) as i32, (y * crate::SCREEN_SCALE) as i32, crate::SCREEN_SCALE as u32, crate::SCREEN_SCALE as u32));
+	    }
+	}
+	self.canvas.present();
+    }
+}