Replace == by is to avoid FutureWarning

Author: Julien

.gitignore

@@ -2,3 +2,4 @@
 /build
 /dist
 /doc/build
+__pycache__

pydc1394/frame.py

@@ -86,7 +86,7 @@ def __array_finalize__(self, img):
 
         If called with an image object, inherit the properties of that image.
         """
-        if img == None:
+        if img is None:
             return
         # do not inherit _frame and _cam since we also get called on copy()
         # and should not hold references to the frame in this case