Bumps Vagrant to v1.7.0
Add Plugin Spec

Reversed engineered for the work I did for vagrant-omnibus here: https://github.com/opscode/vagrant-omnibus/pull/92
Added Error message to language file
Porting over Vagrant version checker

Adapted from code I added for https://github.com/opscode/vagrant-omnibus/
Merge pull request #18 from scottsuch/vagrant17_update

Bump Vagrant to v1.7.0
Merge pull request #19 from petems/add_plugin_spec

Add plugin spec