url_for and routes defined twice

[davidbgk]

Sometimes, you want to define two routes for the same handler, for instance:

@app.route("/url")
@app.route("/old-url")
async def handler():

(Think legacy)

In that case, which route to return with url_for? Maybe only the named one? Maybe a regular redirection for the old route is the correct way to do?

[davidbgk]

Another issue related to it: if you the static extension twice, the generated routes will have the same name too.

[davidbgk]

Fixed in #142