move bytes decoding to callback

Demos/callback/cheese.pyx

@@ -10,4 +10,6 @@ def find(f):
     find_cheeses(callback, <void*>f)
     
 cdef void callback(char *name, void *f):
-    (<object>f)(name)
+    the_name = <bytes> name
+    (<object>f)(the_name.decode('utf-8'))
+    

Demos/callback/run_cheese.py

 import cheese
 
 def report_cheese(name):
-    print("Found cheese: " + name.decode('utf-8'))
+    print("Found cheese: " + name)
 
 cheese.find(report_cheese)
 
+