DRY up Rails Navigation Code
You could create another helper to create your navigation links:

def navigation_link_to(text, path)
  link_to text, path, class: "btn #{active_page(path)}"
end 


Then in your view:

= navigation_link_to 'Home', root_path
= navigation_link_to 'Sign in', sign_in_path
= navigation_link_to 'Account', account_path