Switches from text-format to formatting

[jkachmar]

text-formatting appears to be unmaintained (last commit was 2015, several PRs are sitting unmerged including one that unblocks GHC 8.4). Fortunately it looks like formatting is a drop-in replacement for it.

I've bumped stack.yaml to LTS 11.1 to pull in formatting-6.3.1 and prettyprinter-1.2.0.1, and verified that the project builds and testa pass. I also verified a successful build and test run against nightly-2018-03-18

Note that I can't seem to get cabal2nix to work, so I hand-edited the default.nix file to remove text-format and add formatting, but I'm not entirely sure if that's kosher.

[Gabriella439]

Thanks for doing this! I will fix the build errors, so don't worry

[jkachmar]

Whoops, didn't see your comment! I didn't realize that LTS 9.6 -> LTS 11.1 would bump GHC so I reverted it and added an extra dep for formatting-6.3.1, and ran the tests a few times to get an approximation of what kind of performance effects this would have (negligible, something like 1.53s vs 1.49s after 3 rounds of testing each).

[Gabriella439]

Just merge https://github.com/jkachmar/dhall-haskell/pull/1 into your branch and then CI should pass

[Gabriella439]

Awesome! Thanks for fixing this :)