There's now a new API for invoking the hierarchy layout (hierarchy.nodes) rather
than calling the layout function directly. Calling the new API enables inlining,
which is disabled by default for backwards-compatibility.
This way, we don't need symlinks (which don't work on Windows). This commit also
simplifies the structure of the flare.json file, so that we don't need to tricky
conversion of the JSON map—it can be read directly by the hierarchy layout.
Mike Bostock