Merge pull request #39 from dglaude/patch-1

Update matrix_11x7.py

Author: makermelissa

adafruit_is31fl3731/matrix_11x7.py

@@ -42,8 +42,4 @@ def __init__(self, i2c, address=0x75):
     @staticmethod
     def pixel_addr(x, y):
         """Translate an x,y coordinate to a pixel index."""
-        if x <= 5:
-            r = x * 16 + y
-        else:
-            r = (x - 5) * 16 + y - 8
-        return r
+        return (x << 4) - y + (6 if x <= 5 else -82)