Nobody uses this private method, maybe it is a leftover from some old
refactoring. Let's delete it.

Because it is used as a queue (FIFO), not as a stack (LIFO).

* http://en.wikipedia.org/wiki/Stack_(abstract_data_type)
* http://en.wikipedia.org/wiki/Queue_(data_structure)

Inspired by https://github.com/rails/rails/commit/931ee4186b877856b212b0085cd7bd7f6a4aea67

```ruby

def stat(num)
  start = GC.stat(:total_allocated_object)
  num.times { yield }
  total_obj_count = GC.stat(:total_allocated_object) - start
  puts "#{total_obj_count / num} allocations per call"
end

h = { 'x' => 'y' }

stat(100) { h.     each { |pair| pair } }
stat(100) { h.to_a.each { |pair| pair } }

__END__
1 allocations per call
2 allocations per call
```

The array is sorted in descending order, so there is no point in
iterating further if we met a negative item - all the rest will be
negative too.

When an optimized helper fails to generate, show the full route constraints
in the error message. Previously it would only show the contraints that were
required as part of the path.

Fixes #13592

When generating an unnamed url (i.e. using `url_for` with an options
hash) we should skip anything other than standard Rails routes otherwise
it will match the first mounted application or redirect and generate a
url with query parameters rather than raising an error if the options
hash doesn't match any defined routes.

Fixes #8018

It'd be a nice convention to mark the unused variables like this, now that Ruby 2 will issue no warnings for such vars being unused.

Now that Journey has been integrated into ActionDispatch we can raise
the exception ActionController::UrlGenerationError directly rather than
raising the internal Journey::Router::RoutingError and then have
ActionDispatch::Routing::RouteSet#generate re-raise the exception.

Move the Journey code underneath the ActionDispatch namespace so
that we don't pollute the global namespace with names that may
be used for models.

Fixes rails/journey#49.