Babylon has a two top level nodes: File and Program whereas flow just has Program. This causes two things two happen that prevents comments from being displayed:
1) Because there's a single node, none of following/preceding/enclosing exist. We ran into a TOOD case that we now need to fill. We just need to attach comments to the only node we have: the ast.
2) Both the raw comments and the computed comments are set on the `.comments` field of the object, however, it is being reset after calling `attach`, so we lose the computed comments :( The fix is to use a local variable and delete the comments before calling `attach`.
* new_tests
* move_all_clobbered_tests
* remove all the tests that no longer exist
* re-run flow tests
* Move all the flow tests to tests/flow and prettier to tests/
* Move prettier tests to their own folders
* Add jsfmt files
* run prettier snapshot tests
James Long