[Downloader] Print a message in verbose mode when copying the pod

lib/cocoapods/downloader.rb

@@ -33,9 +33,11 @@ module Pod
       cache = Cache.new(cache_path)
       result = cache.download_pod(request)
       if target
+        UI.message "Copying #{request.name} from `#{result.location}` to #{UI.path target}", '> ' do
           FileUtils.rm_rf target
           FileUtils.cp_r(result.location, target)
         end
+      end
       result
     ensure
       FileUtils.rm_r cache_path if tmp_cache