Make remove tail-call optimized

[jfmengels]

This makes remove tail-call optimized, meaning it will not blow up the stack when working on lists that are too large.

|This also improves performance:](https://github.com/jfmengels/elm-benchmarks/blob/master/src/ImprovingPerformance/ListExtra/Remove.elm)

I also special-cased the case where the element is not found so that we don't unnecessarily recreate the entire list from the accumulator.

I also added tests for remove and applied elm-format (seems like tests weren't properly formatted).

[Chadtech]

Awesome work! Thanks @jfmengels