Fix Either and Maybe ::memoize() not loading everything

[Baptouuuu]

Problem

When one creates a deferred Maybe and then compose it via a flatMap that returns a new deferred Maybe this creates internally a deferred monad containing a deferred monad. When the method memoize is called on it, it returns the underlying deferred monad.

This is problematic because the user thinks the whole composition has been memoized and potential IO operations associated with it have been done. But this is not the case.

The same problem happens with Either.

Solution

When memoize is called on these monads it recursively memoize the underlying monad. This way the recursion stops when a non deferred monad is found.