use immutable as dependency not fork

[hexsprite]

Hey guys - are you open to having a version where immutable-js is a dependency instead of forking it? That way you'll get improvements if any are made in immutable-js

[applitopia]

Thank you for your suggestion, we will definitely consider refactoring this project to eliminate the original immutable-js code and make imports from a separate package instead.

[applitopia]

This package is currently based on latest version of immutable-js@4.0.0-rc.9 which is a release candidate not published in NPM. We will have to wait until facebook fully releases v4.0.0.

[chrisnojima]

Just a heads up rc-10 exist and it seems like 4.0.0 isn't going to happen anytime soon...
(https://github.com/facebook/immutable-js/tree/v4.0.0-rc.10)