Require addressable gem in CurrentPathQuery

The following commit used Addressable to normalize path comparisons:

d6a824c00e

However, it's causing a NameError if the addressable gem is not loaded,
so we're requiring it in this specific location.

lib/capybara/queries/current_path_query.rb

@@ -1,3 +1,5 @@
+require 'addressable'
+
 module Capybara
   # @api private
   module Queries