add small dat file to repo and use it in tests

[jkingslake]

The two tests currently setup load data from a google bucket (these data are in the form of relatively large .dat files).

Simpler tests could use smaller dat files that are stored directly in the repo.

[jkingslake]

#20 will add four .dat files for use in tests. It still remains to write new tests that use them.

[jkingslake]

#20 added these example dat files.