Figure out what the factors are that limit the file size

[waldoj]

There is, inevitably, a file size limit. Figure out what the factors are that create that limit (e.g., memory allocated to APC), and document them, so that folks know what to expect.

(Originally filed as part of #17.)

[davidrs]

I'm using the hosted version to offer an API for openjustice data from the doj in CA.
https://openjustice.doj.ca.gov/data

Some of their datasets are large so it would be good to learn the limits of this. I'll post anything strange I hit.