update build script to eliminate need to install and build with meteor

build.sh

 #!/bin/bash
-source ./build-info.sh
-export METEOR_SETTINGS=$(cat settings.json)
-meteor add rocketchat:livechat
-meteor add rocketchat:hubot
-meteor build --server https://demo.rocket.chat --directory /var/www/rocket.chat
+cd /var/www/rocket.chat
+https://s3.amazonaws.com/rocketchatbuild/demo.rocket.chat-v.latest.tgz" -o rocket.chat.tgz
+tar zxvf rocket.chat.tgz  &&  rm rocket.chat.tgz
 cd /var/www/rocket.chat/bundle/programs/server
 npm install
 cd /var/www/rocket.chat/current