Xeroizer ruby library

Given that Xero (cue the hyperbole about how Xero is great) has just updated their development API and they are planning to do this much more in the future, I have taken this opportunity to create my own ruby-based library for it.

This library builds off the awesome work done by Tim Connor for the first & second API releases.

My version changes things up a bit by:

• adding Partner-application support
• making data-access more ActiveRecord-like (although definitely not feature-complete) 
• simplifying the definition (and redefinition as Xero continues to add to their API) of models to make keeping them up-to-date and testable easier.

I also plan on adding some features to the querying engine to make it easier to filter results whilst staying within the ruby language (and not having to drop into C#).

If you want to get started, check out the README or if you want to dive right into the code, head over to https://github.com/waynerobinson/xeroizer and clone a copy.

Note: This is an alpha-level version of the API. Feel free to increase functionality and test coverage and send me a GitHub pull-request for integration.