Created a basic Bootstrap MenuPresenter class

I created a basic BootstrapMenuPresenter class that is a child of the MenuPresenter class. This class renders a menu that adds the basic css classes required for creating a basic [Bootstrap Tabs Navs menu](http://getbootstrap.com/components/#nav-tabs).

I created some rspec tests for my extensions, but I can't get them to pass, even though I modeled my tests after the ones I found in the menu_presenter_spec.rb tests. Specifically, the ruby interpreter complains about a non-existent variable bootstrap_menu_presenter, even though I declared it in a way that mirrors the way it's declared in the menu_presenter_spec.rb file.

Would anyone be willing to help me fix the issues I'm having in getting my contribution up to refinerycms contribution standards?