Update Version Check for Vagrant 1.6

Vagrant 1.6.0 (and now 1.6.1) has been released change_host_name
API/calls remain unchanged/broken in my testing/knowledge. Made this
change and tested in my set ups, works fine. Should update to Vagrant
1.6.x support without an issue as far as I can tell/know/have tested.
Merge pull request #32 from 24601/master

Update Version Check for Vagrant 1.6