Link to dcos-vagrant rather than playa-mesos.
Link to dcos-vagrant rather than playa-mesos.

This resolves #744.

motusllc/chronos,mesos/chronos,lionelnicolas/chronos,mesos/chronos,motusllc/chronos,motusllc/chronos,mesos/chronos,vixns/chronos,lionelnicolas/chronos,vixns/chronos,lionelnicolas/chronos,vixns/chronos,mesos/chronos,vixns/chronos,motusllc/chronos,lionelnicolas/chronos