data: Add access to route metadata in the templating data. It's available under `route`. Also, rename `slug` to `rel_url`, because it's confusing when `slug` could be the route metadata of the same name as provided by the default page source. The old `slug` is still there for backwards compatibility though.

import os
from invoke import task, run


@task
def genmessages():
    root_dir = 'garcon/messages'
    out_dir = 'piecrust/resources/messages'
    run('python chef.py --root %s bake -o %s' % (root_dir, out_dir))
    os.unlink('piecrust/resources/messages/index.html')