Update for fixed tests
Adjust code style in clientrect
Update style of flow and remove its reliance on `tree`

`tree` is an old API that predates the use of traits. It should be redone.
This commit breaks the dependency on it.
Remove the confusing `tree` API. It should be recreated later.
Incorporate updates for language changes
Merge pull request #412 from pcwalton/detree

Remove the "tree" API and clean up flow a bit