Bug Fixes
- We expose the attachment model so that it can be used in the API
([`5e0b602`](https://github.com/nguaman/licitpy/commit/5e0b60243b64350b2c9bdeac36369960af310e5f))
- We expose the Item, Question, Renewal, and Subcontracting models
([`f0ab927`](https://github.com/nguaman/licitpy/commit/f0ab927b829696818506cf13f95873728d601a5f))