Elixir implementations of Melissa O’Neill’s genuine sieve of Eratosthenes.
Eratosthenes.Eager.sieve/1 is a fairly faithful translation from Haskell to Elixir,
but is less efficient since Elixir lacks Haskell's lazy lists.
Eratosthenes.Lazy.sieve/1 is a more efficient implementation which produces a Stream of primes.