using stub to create test doubles is deprecated, use double directly

spec/browser_spec.rb

@@ -249,7 +249,7 @@ describe Capybara::Webkit::Browser do
   end
 
   it "doesn't try to read an empty response" do
-    connection = stub("connection")
+    connection = double("connection")
     connection.stub(:puts)
     connection.stub(:print)
     connection.stub(:gets).and_return("ok\n", "0\n")

spec/connection_spec.rb

@@ -53,7 +53,7 @@ describe Capybara::Webkit::Connection do
   end
 
   it 'sets appropriate options on its socket' do
-    socket = stub('socket')
+    socket = double('socket')
     TCPSocket.stub(:open).and_return(socket)
     if defined?(Socket::TCP_NODELAY)
       socket.should_receive(:setsockopt).with(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, true)