Update p5-XML-Atom-SimpleFeed to 0.863.

0.863 Thu 10 Sep 2015
[INCOMPATIBLE CHANGE] - Datetime object support now via
->epoch method instead of ->strftime.

  Despite the fact that this is an incompatible change, it
  should actually be a nonevent for almost all users, because
  every datetime module I could find that supports ->strftime
  also supports ->epoch (and vice versa).

  However, the ->strftime methods of many modules are (subtly
  or badly) broken in the face of timezones even as their
  ->epoch methods work right (or else are broken subtly
  enough to escape notice).

  But if you have written your own datetime class, and it
  has a ->strftime method but not an ->epoch method, and
  you pass instance of that class to instance of this module,
  then the feeds you generate that way will now be broken.

  On balance, I believe that this change will unbreak vastly
  more code than it breaks. Therefore I decided to switch.

(kleink)