Parse ISO8601 format strings as datetimes

[brycekbargar]

In FOLIO dates and times are usually RFC3339. During the initial re-implementation I didn't quite understand what that meant and hadn't dug any further because there was a bunch of other changes going into the release. In #77 it was determined that dates from FOLIO are commonly in the less restrictive ISO8601 format. After learning more about RFC3339 and ISO8601 I created a regex which I believe handles all the datetimes that FOLIO can return with two exceptions.

1. While FOLIO claims to store everything in UTC it also claimed to return everything in RFC3339. I don't necessarily trust automatically converting datetimes without an offset to UTC.
2. In the 5C instance some dates are returned that have a decimal indicating there should be fractional seconds but there aren't actually fractional seconds.

Many test cases for both the positive and negative case have been added to verify/document the supported conversion.

There was a latent fault in the sql for datetimes. The returned column was named is_uuid instead of is_datetime. Because the columns are read into python by position and not name this had not caused an error.