Fraction.simplify: Handle zero numerators properly
Add Fraction.toDouble
Extract Fraction canonicalization to fittingly-named method
Add Fraction.equals
Document Fraction.equals
Add and implement TiePlaceAssignment
Add default implementation of assignPlace to TiePlaceAssignment

This version of the method *SHOULD* never be called, since all instances
override it, but I want to ensure that this method is present in the
Enum class, not just in each of the members--that would deny calling
assignPlace on anything but a literal, the way I understand it, since
each literal is an instance of an anonymous class extending the enum.