Replace libdash pretty printer with shasta?

[BolunThompson]

Would it be possible to merge the libdash and shasta pretty printers? There have been multiple PRs (#31, #32) that have had to be duplicated across shasta, libdash ocaml and libdash python.

The necessary way of doing this would be to remove the libdash python pretty printer, and instead require a pass through shasta, since shasta already needs to be able to print its typed ast.

Referenced here.

[BolunThompson]

There’s also #25, which proposes that libdash should return shasta asts, which seems like a sound approach.

[mgree]

The only blocker here is that I would want to move https://github.com/mgree/smoosh forward at the same time. I'm not sure when I'll have time to push on all of that, but it should be a fast enough change.