Lab 3 Inheritance Solution

  Outcomes
* Enhance an existing unit test suite to increase confidence in code correctness.
* Refactor existing highly similar classes by adding a third (super-)class and leveraging inheritance.

  Description
* Look at the code for the two classes given, `TabSeparatedFile` and `CommaSeparatedFile` and refactor the code to try to maximize re-use of common data elements and methods.
* Add new unit tests as needed to utilize new function names, etc.