Fixed equals() method and added hashCode() method for Fraction (both).
Fixed equals() method and added hashCode() method for Complex (both).
Changed HASH_PRIME's.
Fixed equals() method and added hashCode() method for PolyUnit (both).
Changed HASH_PRIME's to be different for each class.
Fixed equals() method and added hashCode() method for Polynomial (both).
Fixed equals() method and added hashCode() method for Matrix(both).
Changed hashCode() method for Matrix to sum Double.hashCode().
Added ZeroDivisionException throws to PolyUnit.
Added PolyUnitTest