Tests for the maybe type implemented.
AsNullable() extension added for value-typed maybes.
Additional Maybe tests.
Readme updated.
SingleAsMaybe() and FirstAsMaybe() extensions for IEnumerable implemented.
Conversion from IFinalList<T> to IImmutableList<T> implemented as extension (to maintain covariance).
ExistingOnly() extension for enumerables of IMaybe implemented.
IMaybe.SelectMany() implemented for completeness.
License added.