Merge pull request #13 from mmerkes/item_requests

Item requests
Breaking changes to API, new API version: 0.0.4
Update POST /items to handle creating an array of items
Add POST and GET /items/:item/requests routes, including specs, and update README accordingly
Add routes for GET, PUT, and DELETE /items/:item/requests/:request, including specs
Complete GET /users/:username/my-requests and /neighbor-requests as well as specs
Refactor POST /items to handle batches more efficiently
Merge pull request #14 from mmerkes/item_requests

Item requests