Drop elm- from package name

[Janis Voigtländer]

As per this: elm-community/guidelines#27.

[Abadi Kurniawan]

Same with maybe-extra, I'm gonna need help from owner to rename the repo, then I can publish the package.

[Janis Voigtländer]

Done. What was the other repository where it's also needed? (I think you took over three, right?)

[Abadi Kurniawan]

Thanks!
I took over elm-list-extra, but that one is already published, so we're gonna need to mark the old one deprecated, and create a new repo with the new name.

[Abadi Kurniawan]

It's published! http://package.elm-lang.org/packages/elm-community/result-extra/1.0.0/