message: add createPrivateConversation
diff: @@ -313,6 +313,16 @@ module.exports = function(botkit, config) {
  botkit.createConversation(this, message, cb);
  };
  + bot.createPrivateConversation = function(message, cb) {
  + bot.api.im.open({ user: message.user }, function(err, channel) {
  + if (err) return cb(err);
  +
  + message.channel = channel.channel.id;
  +
  + botkit.createConversation(bot, message, cb);
  + });
  + };
  +
  bot.createConversationInThread = function(message, cb) {
  // make replies happen in a thread
  if (!message.thread_ts) {
  