Add update script; works like bootstrap script

Much copy and paste and should definitely be combined with the bootstrap script.
Oh well...

update.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+
+# UPDATE SCRIPT - on a more clever day, I might merge this with bootstrap.sh
+# Can take a single param to allow a specific branch to be installed
+BRANCH=$1
+
+# TO BE RUN AS ROOT
+if [[ $(/usr/bin/id -u) -ne 0 ]]; then
+  echo "This script must be run as root"
+  exit
+fi
+
+# CLONE PUPPET REPOSITORY
+cd /tmp
+rm -rf puppet
+git clone https://github.com/atomaka/tc362.git puppet
+cd puppet
+
+if [ "$BRANCH" != "" ]; then
+  git fetch
+  git checkout $BRANCH
+fi
+
+# INSTALL MODULES
+librarian-puppet install
+
+# RUN MANIFEST
+puppet apply manifests/site.pp --modulepath=modules/