Fix incorrect namespace of #named_routes.

ref #1095
I fixed #named_routes behavior.

BTW, should we fix `url` behavior?
If so, I'm going to modify the behavior in this way.
```ruby
url(:cap_alerts, :index) #=> "/cap_alerts"
url(:cap, :alerts, :index) #=> UnrecognizedException
url(:cap, :alerts_index) #=> UnrecognizedException
```