Dead links in README

[jjst]

The README states:

---

If you are looking for a way to store information, you should take a look into local-storage or session-storage instead.

---

But when trying to access those links package.elm-lang.org says:

Could not find any versions of package elm-lang/local-storage

[jjst]

Oh, after some googling looks like this is still WIP: https://github.com/elm-lang/local-storage Putting in there in case people are wondering why the links are dead.

[felixakiragreen]

And now it's https://github.com/elm-lang/persistent-cache