Add functor class to the index.
Move composition and identity to IsFunctor.
Prove that func-equality is an isomorphism.
Prove hlevel closure property for graph morphisms.
Add category of monoids.
Refactor definition of injectivity.
Add left cancellation for natural numbers.
Remove old groupoid modules.
Factor out IsGroupoid structure.
Add definition of group.
Add definition of group morphism.
Split definition of groupoid into separate modules.
Make uses of dependent function composition explicit.
Set up overloading for Graph.
Add overloadable function composition.
Remove category.class.
Use overloading mechanism for category methods.
Overload composition for categories.
Move graph morphisms to a separate module.
Overload composition of graph morphisms.