Fixed Vagrant 1.7 compatibility issue.

Vagrant started to call get_state action inside 'vagrant up' command (https://github.com/mitchellh/vagrant/issues/4513).
`vagrant up` fails with `There are errors in the configuration of this machine` error, if vagrant boxes are downloaded from remote server, and local Vagrantfile don't contain vSphere connection info.
Add a spec for handling connection info from a box
Merge branch 'mkuzmin-get-state'
Update README for pull request #111