Modify LEDBorg code example to work with Python2

See #127

src/en/overlay/piborg-ledborg.md

@@ -50,15 +50,15 @@ lb = LedBorg()
 while True:
     r, g, b = 0, 0, 0
     for i in range(100):
-        r = i / 100
+        r = i / 100.0
         lb.value = (r, g, b)
         sleep(0.01)
     for i in range(100):
-        g = i / 100
+        g = i / 100.0
         sleep(0.01)
         lb.value = (r, g, b)
     for i in range(100):
-        b = i / 100
+        b = i / 100.0
         lb.value = (r, g, b)
         sleep(0.01)
 ```