Add support for Elm

[mrmurphy]

Hoping I did this the right way. I just followed the example of the merged PR for supporting stylish-haskell.

Caveat: I don't like that the url for elm-format is hard-coded in the .travis.yml file, but the tool is new enough that it doesn't exist in brew yet.

[Glavin001]

I would accept if this works for Travis CI. Currently it fails: https://travis-ci.org/Glavin001/atom-beautify/builds/96061019

Looks great so far! Once tests are passing I'll take a closer look at the rest of the code, but I looked over it briefly and was definitely on the right track.

[mrmurphy]

@Glavin001 Thanks! I solved the initial Travis failures, but now it appears to be failing on the titanium-style-sheets test. Any hints about how to proceed from here?

I haven't been able to run the tests, locally yet. I open the atom-beautifier folder in Atom, and then I run Window: Run Package Specs, but then a console pops up and I just see the error: AssertionError: missing path

[Glavin001]

I'll fix the unrelated failing tests right now -- Pretty Diff was likely updated again and broke those tests 😜 .

There is also a linting issue for your Elm code that could be fixed in the meantime 😄 .

[Glavin001]

I pushed fixes for the failing tests. If you merge and I can see that your tests for Elm are passing, I will merge anyway 😄. Also be sure to run npm run docs and commit the documentation, too! Thanks.

[mrmurphy]

Whoops! Sorry about that lint error! I've rebase on master, and I've fixed the linter error.

And wahoo! Looks like Travis passed!

[Glavin001]

Please remove this file, or move to the test directory.

[mrmurphy]

Thanks for those detailed comments! I've committed the docs, and I think I've addressed all of your comments.

[Glavin001]

Beautiful! Thank you for contributing!

[Glavin001]

Published to v0.28.20