Refactors the creation of attributes for resources

* Attribute accessors are automatically created for any property defined in the API schema that does not already exist
* Attribute accessors are NO LONGER created for properties passed in to #initialize that are not part of the API schema. If you really want this behavior, you can manually define them in the class definition with `attr_accessor :foo`
* Added a few additional tests to ensure no regressions in regards to adding accessors to *all* subclasses of Resource
* Fixes a bug around schema property to class name matching when an underscore is involved (which was embarrasing…)
Version bump to 0.0.8