Deprecate the :sinatra mode

* I took the conservative approach here: the sinatra code could
  be removed but that'd cause a regression. (using Sinatra::Application
  when `app` is not defined)

* I left the sinatra tests for now; they should be removed
  once we're fully confident with rack session ones.

lib/webrat/core/session.rb

@@ -18,14 +18,17 @@ def self.session_class
       RailsSession
     when :merb
       MerbSession
+    when :rack
+      RackSession
+    when :sinatra
+      warn("The :sinatra mode is deprecated. Please use :rack instead")
+      SinatraSession
     when :selenium
       SeleniumSession
     when :sinatra
       SinatraSession
     when :mechanize
       MechanizeSession
-    when :rack
-      RackSession
     else
       raise WebratError.new(<<-STR)
 Unknown Webrat mode: #{Webrat.configuration.mode.inspect}

lib/webrat/sinatra.rb

@@ -1,41 +1,11 @@
 require "webrat/rack"
-require "sinatra/test"
 
 module Webrat
-  class SinatraSession
-    include Sinatra::Test
-
+  class SinatraSession < RackSession
     def initialize(context)
       app = context.respond_to?(:app) ? context.app : Sinatra::Application
 
-      @browser = Sinatra::TestHarness.new(app)
-    end
-
-    %w(get head post put delete).each do |verb|
-      class_eval <<-RUBY
-        def #{verb}(path, data, headers = {})
-          params = data.inject({}) do |data, (key,value)|
-            data[key] = Rack::Utils.unescape(value)
-            data
-          end
-          headers["HTTP_HOST"] = "www.example.com"
-          @browser.#{verb}(path, params, headers)
-        end
-      RUBY
-    end
-
-    def response_body
-      @browser.body
+      super(Rack::Test::Session.new(app))
     end
-
-    def response_code
-      @browser.response.status
-    end
-
-    private
-
-      def response
-        @browser.response
-      end
   end
 end