Move immutable and seamless-immutable to peer dependencies

[maxmalov]

The original discussion: #296

Currently, I use connected-react-router, redux-form and the project doesn't depend on immutable at all. But it seems like redux-form is pretty eager for immutable library and if it presents inside node_modules it will be included in the bundle, which is pretty confusing. I'm not sure what was the purpose to include immutable and seamless-immutable in the library dependencies (keeping in mind that redux and react-router related stuff lives in peerDependencies), so these are breaking changes. Anyway everyone who wants immutable or seamless-immutable version of this package already has these packages installed, so it won't be a big issue for them to migrate.

[supasate]

LGTM. Thanks!

[ascartabelli]

Just curious: shouldn't optionalDependencies be a more suitable place than peerDependencies for those?

[maxmalov]

Optional dependencies work when the code handles cases when they are not installed https://npm.github.io/using-pkgs-docs/package-json/types/optionaldependencies.html, which can't be applied to connected-react-router/immutable and connected-react-router/seamless-immutable

[ascartabelli]

@maxmalov Sorry for the very late answer and yes, I do understand your reasoning. Still connected-react-router/immutable and connected-react-router/seamless-immutable are just an option, not the "default" exports.
My little pet peeve, here, is that if every library adopted your reasoning we would end with endless, and useless, warnings in the console while using npm.

[Methuselah96]

It seems like that connected-react-router/immutable and connected-react-router/seamless-immutable should be release as separate packages in order to accurately represent their dependencies.

@supasate Has there been any thought of releasing them as separate packages?