Only filter routes with same number of bindings

[danschultzer]

Resolves #291

When a route exists with the same helper alias and controller action, the length of bindings will also be checked. This ensure that the following won't be filtered out:

  scope "/" do
    pipe_through [:browser]

    pow_routes()
    pow_extension_routes()
    pow_assent_routes()
  end

  scope "/:locale" do
    pipe_through [:browser]

    pow_routes()
    pow_extension_routes()
    pow_assent_routes()
  end

The first set of helper aliases in the above is different from the second set so there are no conflicts.