Fix small error in README
Fix small error in README

The paths to the test from the Mesos getting started guide were just slightly incorrect. Fixed them so that users can copy the commands directly from the README without any errors.
prasincs/vagrant-mesos,hippolin/vagrant-mesos,cgvarela/vagrant-mesos,emccode/vagrant,dchesterman/vagrant-mesos,emccode/vagrant,hippolin/vagrant-mesos,dchesterman/vagrant-mesos,scorpionis/vagrant-mesos,codedellemc/vagrant,mesosphere/vagrant-mesos,fonhorst/vagrant-mesos,codedellemc/vagrant,scorpionis/vagrant-mesos,cgvarela/vagrant-mesos,codedellemc/vagrant,fonhorst/vagrant-mesos,mesosphere/vagrant-mesos,afrantisak/vagrant-mesos,yoeluk/vagrant-mesos,yoeluk/vagrant-mesos,everpeace/vagrant-mesos,fonhorst/vagrant-mesos,yoeluk/vagrant-mesos,scorpionis/vagrant-mesos,afrantisak/vagrant-mesos,dchesterman/vagrant-mesos,jonasrosland/vagrant-mesos,everpeace/vagrant-mesos,mesosphere/vagrant-mesos,hippolin/vagrant-mesos,prasincs/vagrant-mesos,afrantisak/vagrant-mesos,cgvarela/vagrant-mesos,prasincs/vagrant-mesos,jonasrosland/vagrant-mesos,emccode/vagrant,everpeace/vagrant-mesos,jonasrosland/vagrant-mesos