creating a morphism module
realized that exposing the elements of my morphisms doesnt really
help b/c a cata going to an ana is going to be equivalent to normal
composition (no point to try to merge them).  while a ana to a cata
can be optimized with a composition, you might as well just do it
manually with a hylo
added anamorphism
implemented catamorphism
implemented hylomorphism
fixed minor issue with morphism

added tests for morphism
removed todo
added some comments for the input of hylo