Fix _getRequiredProducts/getInputProductID on old DB (Closes #20)

[jtniehof]

_getRequiredProducts called getInputProductID with a particular kwarg forcing return of the yesterday-count and tomorrow-count, which aren't in the old database. This PR tests the call with this kwarg and fixes on old databases, returning 0 for both yesterday and tomorrow, so downstream code should work just as it does for newer databases. Closes #20.

PR Checklist

• [X] Pull request has descriptive title
• [X] Pull request gives overview of changes
• [X] New code has inline comments where necessary
• [X] (N/A) Any new modules, functions or classes have docstrings consistent with dbprocessing style
• [X] (N/A) Major new functionality has appropriate Sphinx documentation
• [X] (N/A) Added an entry to CHANGELOG if fixing a major bug or providing a major new feature
• [X] New features and bug fixes should have unit tests
• [X] Relevant issues are linked in the description (e.g. See issue # or Closes #)

[jtniehof]

I'd consider this an urgent fix where the PR doesn't have to stay open just to allow for commenting.