Inline main_app routes for layout

I have big and complicated layout in my app, and I don't want to edit it with all this `main_app.whatever_path`. So I made a solution first seen at https://github.com/KatanaCode/blogit

Create a file `config/initializers/rapifire.rb` with following code (the feature is off by default):

```ruby
Rapidfire.config do |config|
  config.inline_main_app_named_routes = true
end
```

And voila.

The problem is similar to that issue: https://github.com/code-mancers/rapidfire/issues/16
i need to think about this. adding `method_missing` in a helper sounds like we are doing something wrong here: `ApplicationHelper` is a module which rails mixes in other classes (which we dont know). So, injecting `method_missing` should be done with some caution.