Upgrading elm from 0.16 to 0.17 using Mac binary

[aldhsu]

Conditions:

• Install elm 0.16 from Mac binary
• Run script to delete references
• Install elm 0.17 from Mac binary

  Problem:

Upgrading elm from binary and running package install on a new project returns error:

• Error: Unable to find a set of packages that will work with your constraints.

  Solution:

Stale package is left in ~/.elm and builds a faulty elm-package.json and will prevent installing any further dependencies. I just deleted the folder and it should probably be included in the script.

[jvoigtlaender]

This is not going to be needed with any version beyond 0.17, because of this: https://github.com/elm-lang/elm-package/commit/645fdb76de86b068857dab4303acbe9f9813178e.

That is, when Elm 0.17.1 or Elm 0.18 comes out, the "stale" ~/.elm/package will not cause any problems, because the new version will use ~/.elm/0.17.1/package or ~/.elm/0.18/package directories.

[evancz]

I don't have bandwidth to backport a fix. It's just gonna suck for past versions :/

[aldhsu]

That's fine. Thanks for Elm! I put this issue up in case anyone else runs into it.