A generic Amazon E-commerce REST API with configurable default options and
method call options. It uses Hpricot to parse the XML output. Use Response and
Element wrapper classes for easy access to the XML elements, and it supports
ECS 4.0.

It is generic, so you can extend Amazon::Ecs to support the other not-
implemented operations easily; and the response object just wraps around
Hpricot element object, instead of providing one-to-one object/attributes to
XML elements map.

With that, if in the future, there is a change in REST XML output structure,
no changes will be required on amazon-ecs, instead you just need to change
your element path.
