1.1.1: Fix polynomial degree lookup error (OSK-7) (#8)

Motivation
----
Some PolynomialMath and polynomial index functions are failing due to
index lookups not properly accounting for packing, when they should be

Modifications
----
* Adjusted Polynomial get by degree method to better handle lookups when
in either a pack or unpacked state
* Updated PolynomialMath to use the correct method for a couple of
functions using a direct indexer by mistake
* Updated UnitTests to catch current known issues

Result
----
Polynomial math and index lookps work as expected

Fixes #7