It's not really needed.

F seems to be the canonical name for the functor of an F-coalgebra.

Instead of a tuple of a Bool and an Int, include the Bool value in the
Int as its least significant bit.

We don't need to know the count of edges that go outside of the block of
interest. It only matters whether there is one, so that we can correctly
return H3 in update.

Those functors really require the inverse operation to perform as
required. A separate functor for monoids that aren't groups is
feasable, but would not satisfy the runtime complexity requirements.

We can't split them anyways, might as well skip the work done by
updateBlock and splitBlock.

This can make the algorithm roughly twice as fast on some inputs.

This makes the interface easier to comprehend and write tests for.
There is now an extra function `addBlocksToQueue` that handles the
queue stuff.