curl_command: Add support for --user option

Author: bastelfreak

lib/voxpupuli/acceptance/serverspec_extensions/curl_command.rb

@@ -33,7 +33,7 @@ def curl_command
 
           @options.each do |option, value|
             case option
-            when :cacert, :cert, :key
+            when :cacert, :cert, :key, :user
               command += " --#{option} '#{value}'"
             when :headers
               value.each do |header, header_value|