Added effect "snake".

include/effect_snake.h

@@ -0,0 +1,21 @@
+#ifndef effect_snake_H
+#define effect_snake_H
+
+#include "Effect.h"
+#include "prototypes.h"
+
+class SnakeEffect : public Effect {
+private:
+	Coords coords;
+	uint8_t direction;
+	uint8_t hue;
+	uint8_t run;
+	Window window = {0, 0, LED_WIDTH, LED_HEIGHT-6};
+public:
+	void loop();
+	boolean valid_position(Coords c);
+	Coords update_position(Coords c, uint8_t direction);
+	boolean can_be_shown_with_clock();
+};
+
+#endif