Decide the API style

[fangpenlin]

The current REST API design is pretty much like what I mentioned in #33 (comment) . I try to make it looks like Balanced API, however, there are something different from details to details.

The Balanced API uses URI as the ID for passing around, I don't know the design rationale here (about version distinguishing?). Maybe we can adjust it to do the same way.

Also, for Balanced API, some relative record will be returned when retrieving one record. For example, you get a Debit, there will be customer data or something like that in the response json body. I think the rationale here is for efficiency? (save some extra requests?). Anyway, I can also make the same to billy API, just need some rules of thumb to decide which relative records to include, and how deep it should be.

[mjallday]

We use an internal framework called l00b that could make this very easy to develop in a similar style to Balanced's API. Open sourcing that framework could really help make this task easy.

[steveklabnik]

I don't know the design rationale here

URLs are globally unique IDs, whereas ID numbers are not.