Update Vagrantfile

Updated for the installation of curl and omnibus automatically for Ubuntu.
bumped default version of sensu to 0.11.3-1
Merge pull request #190 from portertech/sensu-0.11.3-1

bumped default version of sensu to 0.11.3-1
Merge pull request #188 from jjasghar/patch-1

Update Vagrantfile