Fixed: testing DateTime with their RFC850 representation

Creating a DateTime with, e.g.:
"Wed, 21 Jul 2013 00:00:00 America/Guadeloupe" will create an object
with "America/Guadeloupe" timezone, but once store in RFC850 format, the
exact timezone used is lost: "Wednesday, 24-Jul-13 00:00:00 AST"
Creating a DateTime from this representation will result in a DateTime
object with "AST" timezone.

The tests assertion will fail comparing "America/Guadeloupe" with "AST"
although the DateTime object should be considered equal.