Console helper

Add a `console` helper for Action View. Just put `<% console %>` any where in the view to trigger the console at the bottom of the page.
I think this should be done in a lazy-load hook:

```ruby
ActiveSupport.on_load :action_view do
  include WebConsole::ViewHelpers
end
```

More info about lazy-load hooks: http://simonecarletti.com/blog/2011/04/understanding-ruby-and-rails-lazy-load-hooks/