Force encoding to UTF-8 for response on ruby 1.9.x, as we receive UTF…

…-8 QString only from server.

This fix the failing spec related to UTF-8 encoding checks. It's not the best solution,
but TCPSocket on Ruby 1.9.x defaults to ASCII-8bit, the server sends responses as
UTF-8 encoded string only.

lib/capybara/driver/webkit/browser.rb

@@ -103,7 +103,12 @@ def check
 
     def read_response
       response_length = @socket.gets.to_i
-      @socket.read(response_length)
+      response = @socket.read(response_length)
+      if response.respond_to?(:encoding)
+        response.force_encoding "UTF-8"
+      else
+        response
+      end
     end
   end
 end