The 4 byte limit is starting to wrap around; some complaints are being seen
online, e.g.
https://stackoverflow.com/questions/34477248/rails-paperclip-rangeerror/47999887#47999887 .
Use `#sql_type` instead of `#type` in the tests. The `#type` is the category --
string, integer, datetime -- but the `#sql_type` is the storage specifics --
`TEXT`, `VARCHAR`, `BIGINT`, `DATE. Switch to the `#sql_type` so we can be sure
it's being stored correctly.
