Test records should be converted to plaintext

[urda]

Test data should be left in plaintext format for easier debugging. Currently, some test records are stored as actual NistBeaconValue objects. This makes debugging hard as loading the test data library will hit any breakpoints one might enter inside of NistBeaconValue.

Records for testing should all be converted, and loaded from, plain text.

You can see the current records, at time of this issue's creation, here:

https://github.com/urda/nistbeacon/blob/a3ad356f6a55857b79062766a2f3cbe3fe296abb/tests/test_data/nist_records.py

[urda]

Looks like there is only a handful of records to port, starting work.

[urda]

This was added with #30