[FEATURE] Compatible with PHP 5.3; Adds JsonSerializable interface workaround;

Have not tested on versions below PHP 5.3
Merge pull request #4 from xmdevelopmentsinternational/master

Update ValidAddress.class.php
Merge pull request #6 from rclarkburns/legacy

Adds JsonSerializable interface workaround

Thanks for making these changes! I'm going to close out your issue #5 with this merge.
update to reflect new docTypes in service version 14.4
merged and added new doctype values
added line level taxOverride