Add support for the vagrant-cachier plugin

Change-Id: Id3aeaa16e062f764412bd6c5fd9460b5867333a9

README.md

@@ -88,12 +88,18 @@ When someone updates the config, this process should allow you to bring up an up
 - `vagrant up`
 
 ## Improving Provisioning Speed
-The slowest part of the provisioning process is the downloading of deb packages. To speed this up a local apt-cacher-ng can be used.
-### Linux (Ubuntu)
+
+The slowest part of the provisioning process is the downloading of deb packages.
+
+### Local cache
+
+To speed this up a local apt-cacher-ng can be used.
+
+#### Linux (Ubuntu)
 ```
 sudo apt-get install apt-cacher-ng
 ```
-### MacOS
+#### MacOS
 ```
 brew install apt-cacher-ng
 ```
@@ -102,6 +108,16 @@ That is all that is needed.  From now on, the cache will be used.
 
 A report from the cache is found at http://localhost:3142/acng-report.html
 
+### vagrant-cachier
+
+Instead of using apt-cacher-ng you can also use the Vagrant plugin
+`vagrant-cachier` available at https://github.com/fgrehm/vagrant-cachier. To
+use it with this Vagrant box you simply have to install the plugin.
+
+```
+sudo vagrant plugin install vagrant-cachier
+```
+
 ## Cookbook Development
 
 To develop cookbook changes with Vagrant:

Vagrantfile

@@ -7,6 +7,10 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
   # Settings for all vms
   config.berkshelf.enabled = true
 
+  if Vagrant.has_plugin?("vagrant-cachier")
+    config.cache.scope = :box
+  end
+
   # Handle local proxy settings
   if Vagrant.has_plugin?("vagrant-proxyconf")
     if ENV["http_proxy"]