First version of elasticsearch vagrant cluster

Vagrantfile
VMs configuration (elasticsearch.yml)
Script to run the cluster
Adding information in the README
Adding information in the README
Renaming script to launch cluster
Renaming script to launch elasticsearch
Fixing provisionning problem
gitignore
vagrant cloud box url
Updating base box name to match vagrantcloud config
Adding information in the README
Adding information in the README
Merging develop into master