Use resource IDs for singular resources in the new API

With the [new API], calls to singular resources require their resource IDs in the request path. (The linked post states that the current endpoints will be shut off in a few months.) This fork just passes resource IDs via has_resource and prepends them to singular resource ID in the request URL. It should fall back to the old style URL for resources that don't pass an ID.

[new API]: http://www.giantbomb.com/forums/api-developers-3017/the-new-api-almost-the-same-as-the-old-api-1423775/