Fix regression in #52.

We accidentally stopped filtering out machines from other providers.
only update hosts file if it has changed - for both host and guest
Merge pull request #79 from pbitty/fix_pr52_regression

Fix regression in #52.
Merge pull request #78 from thematthopkins/less_sudo_2

only update hosts file if it has changed - for both host and guest

Closes #68.
Replaced deprecated config_global with vagrantfile.config
Fixes introduced error running vagrant hostmanager command
Merge pull request #81 from januzis/vagrant-1.5-support

Replaced deprecated config_global with vagrantfile.config to support vagrant 1.5 API