add kvm support

Signed-off-by: Hiroshi Miura <miurahr@linux.com>

README.md

@@ -41,6 +41,7 @@ http://fgrehm.viewdocs.io/vagrant-cachier.
 * [vagrant-lxc](https://github.com/fgrehm/vagrant-lxc)
 * [VMware providers](http://www.vagrantup.com/vmware) with NFS enabled (See
   [GH-24](https://github.com/fgrehm/vagrant-cachier/issues/24) for more info)
+* [vagrant-kvm]
 
 
 ## Contributing

lib/vagrant-cachier/plugin.rb

@@ -81,6 +81,12 @@ module VagrantPlugins
           require 'vagrant-lxc/action'
           hook.before Vagrant::LXC::Action::Boot, Action::EnsureSingleCacheRoot
         end
+
+        if defined?(Vagrant::ProviderKVM)
+          # XXX
+          require 'vagrant-kvm/action'
+          hook.before Vagrant::PrividerKVM::Action::Boot, Action::EnsureSingleCacheRoot
+        end
       end
       action_hook 'ensure-single-cache-root-exists-on-up',     :machine_action_up,     &ensure_single_cache_root
       action_hook 'ensure-single-cache-root-exists-on-reload', :machine_action_reload, &ensure_single_cache_root