Added a VirtueMart plugin

VirtueMart plugin and instructions
Merge pull request #1 from cavirtex/master

Merge latest changes (Drupal support)
Added ZenCart plugin

Added a plugin for ZenCart as well as installation instructions.
Added osCommerce support

Added support for osCommerce, and instructions for installing the
module.
Merge pull request #8 from aaronkuchma/master

Added support for VirtueMart, ZenCart, and osCommerce
Updated readme with zen cart, oscommerce and virtuemart
Merge pull request #11 from tomtom25/master

Updated readme with zen cart, oscommerce and virtuemart
Merge branch 'master' of https://github.com/cavirtex/merchants

Upstream sync
Added OpenCart support