Fix up errors in previous merge

- Fix ratio in LED color for yellow on EV3
- Add missing BLACK color for rPi

Author: rhempel

ev3dev/brickpi.py

@@ -53,6 +53,7 @@ class Leds(object):
     LED1 = ( blue_led1, )
     LED2 = ( blue_led2, )
 
+    BLACK = ( 0, )
     BLUE = ( 1, )
 
     @staticmethod

ev3dev/ev3.py

@@ -55,11 +55,12 @@ class Leds(object):
     LEFT = ( red_left, green_left, )
     RIGHT = ( red_right, green_right, )
 
+    BLACK = ( 0, 0, )
     RED = ( 1, 0, )
     GREEN = ( 0, 1, )
     AMBER = ( 1, 1, )
     ORANGE = ( 1, 0.5, )
-    YELLOW = ( 0.5, 1, )
+    YELLOW = ( 0.1, 1, )
 
     @staticmethod
     def set_color(group, color, pct=1):