Planned for 0.10.0: Drop official support for Elm 0.17,0.18

Version 0.10.0 (and possible starting in the 0.9.* experimental series), only Elm 0.19 will be supported. This will help simplify upgrading the parser (which should give some huge performance improvements).

Folks who are still using Elm 0.18 can stick with elm-format 0.8.*.

Start by locating the parser and the code paths that support Elm 0.17 and 0.18. Confirm how Elm 0.19 support is represented, then remove the older support while preserving Elm 0.19 formatting and verify the relevant test suite.

Written by the indexing model from the issue text.