Upgrade sensu

DO NOT MERGE

As we dont use something like https://github.com/adrienthebo/r10k, I think the
best way to deploy this will be to deploy from the branch, before merging to 
master

Planned deploy strategy - 

 - Stop sensu on all machines using fabric

 - flush redis

 - deploy sensu to monitoring machine and upgrade it

 - deploy sensu to other machines in environment
Umm, that's a path rather than vhost?