Allow toggling between css or xpath as the default selecto style.

lib/capybara/dsl.rb

@@ -1,6 +1,7 @@
 module Capybara
   class << self
     attr_writer :default_driver, :current_driver, :javascript_driver
+    attr_writer :default_selector
 
     attr_accessor :app
 
@@ -29,6 +30,10 @@ module Capybara
       @session_pool = nil
     end
 
+    def default_selector
+      @default_selector ||= :xpath
+    end
+
   private
 
     def session_pool

lib/capybara/session.rb

@@ -92,7 +92,7 @@ class Capybara::Session
   end
   
   def within(kind, scope=nil)
-    kind, scope = :xpath, kind unless scope
+    kind, scope = Capybara.default_selector, kind unless scope
     scope = css_to_xpath(scope) if kind == :css
     raise Capybara::ElementNotFound, "scope '#{scope}' not found on page" if find(scope).empty?
     scopes.push(scope)