Update changelog
Read the bundle's info dictionary directly

If there is already a bundle in memory for the given URL the previous
instance will be returned, with a cached info dictionary.
Use unsafe_unretained reference to work around 10.9 performance issue

10.9 uses a weaker hashing algorithm for weak reference pointers,
leading to trivial collisions within the hash table. This results in a
significant performance penalty for the large number of STASymbols
created with weak references. Switch to unsafe_unretained until this is
fixed.