Write unit tests for model and benchmark ingest BMIs

[mdpiper]

In #6, I stubbed out BMIs for the ModelIngestTool and the BenchmarkIngestTool (and actually the BMIs are fairly complete, it's the underlying tool code that hasn't been written); however, I didn't write unit tests for them. This needs to be done.

[mdpiper]

Tests for ModelIngestTool were completed in 05f0c94.