Port to winrm v2.

WinRb/WinRM#191

lib/specinfra/backend/winrm.rb

@@ -11,18 +11,20 @@ def run_command(cmd, opts={})
         script = create_script(cmd)
         winrm = get_config(:winrm)
 
-        result = winrm.powershell(script)
-        stdout, stderr = [:stdout, :stderr].map do |s|
-          result[:data].select {|item| item.key? s}.map {|item| item[s]}.join
-        end
-        result[:exitcode] = 1 if result[:exitcode] == 0 and !stderr.empty?
+        winrm.shell(:powershell) do |shell|
+          result = shell.run(script)
+          stdout = result.stdout.to_s
+          stderr = result.stderr.to_s
 
-        if @example
-          @example.metadata[:command] = script
-          @example.metadata[:stdout]  = stdout + stderr
-        end
+          result.exitcode = 1 if result.exitcode == 0 and !stderr.empty?
 
-        CommandResult.new :stdout => stdout, :stderr => stderr, :exit_status => result[:exitcode]
+          if @example
+            @example.metadata[:command] = script
+            @example.metadata[:stdout]  = stdout + stderr
+          end
+
+          CommandResult.new :stdout => stdout, :stderr => stderr, :exit_status => result.exitcode
+        end
       end
     end
   end