Add tests and code for entitization

[james-trimarco]

This adds a simple algorithm that looks at every line in the input and asks: "Have I seen this person before?"

If yes, we write a new row to the employees table. Then we write a row to statuses with the employee ID from that row.

If no, we don't add anything to employees. We find the correct employee id and add a row to statuses with that id.