Added test rake task and a simple test
Add ActiveRecord-ish associations and a few more API objects

* Add Duder::Base to abstract some of the common resource logic
* Add Duder::Character
  * Has many friends and enemies, which are loaded on demand
* Add Duder::Company
* Add Duder::Associations with a simple has_many association
* Add Duder::Exceptions
* Add Duder::Resource, the base API client