Pay more attention to order of elements (e.g. entries) on output

Many feed readers will present the entries in the order they are
given.  For the user of this library to be able to influence that
order, the items must be outputted in the same order they are listed
in the feed.entries field.
Merge pull request #42 from Chris00/master

Pay more attention to order of elements (e.g. entries) on output