Vertical align comments
Fix return of error condition when item_sort_key is not a function
Fix initialization, INCREFing members right after assignment
Cherry pick the fix for https://github.com/simplejson/simplejson/issues/98

Cherry pick part of upstream b7486b82233ed2ec1a614dcf8944d376d12d04bf,
complementing 9169e0841e697c33d81b2365981cbaf317b6a805.
Fix datetime-related arguments passing to the class constructor
Micro-optimization, using local variables instead of globals
Update CHANGES.rst
Release 0.4