Update to elm-test 2.0

[tgecho]

This is an example of what an exercise upgraded to elm-test 2.0 looks like (fixes #95). Among other highlights, I've reenabled the node elm-test runner workflow (npm install -g elm-test) as before, so the output is much nicer and by ditching the runtests scripts we can close #76.

• Update the rest of the exercises
• Update the installation/running docs
• Get a 👍 from at least one other human being

[lpil]

I think this syntax is the convention the Elm Test community are trying to promote:

test "square Accumulate" <|
    \() -> 
        accumulate square [ 1, 2, 3 ]
            |> Expect.equal [ 1, 4, 9 ] 

I recognise this is probably hard to change without lots of busy work though.

[tgecho]

Yeah... To be honest I was able to do 99% of this via regex flavored find/replace because I was keeping the existing closing paren at the end of each test. Switching to that style will require a bit more work. That's really my strongest objection :)

[lpil]

I think we should do it, but perhaps it's something we can leave for a later pull request, or just do incrementally.

[tgecho]

Ok, you got me. I figured how to get 95% of it in bulk, and elm-format helped me sort out the rest pretty quickly.

[lpil]

I like where this is going so far :)

Do we run Elm Format on the exercises?

[tgecho]

Not in CI. There's an issue for that (#47), but no one has bothered to try installing it in Travis yet.

[tgecho]

Anyone have any objections to merging this (squashed, etc...)? @lpil @parkerl @lukewestby

[lpil]

Looks great! Thank you for doing all this work.