Fix missing connection causing specs to fail when run alone

An API connection has to be instantiated, but the spec file did not do this.
Extract methods into Resourceable
Add ProductCollection
Abstract behavior into AbstractResourceCollection
Tell git to ignore all test scripts
Add shared examples for Resourceable and refactor

- Moved AbstractResource and AbstractCollection tests into Resourceable shared examples
- Moved #resource_class to .resource_class in all classes
- Added pending tests for AbstractResource, which is currently tested via its subclasses
Remove redundant method from AbstractResourceCollection
Merge pull request #23 from allolex/product_collection

Create product collection for efficient processing

Plus, some other refactoring and optimizations.