adding rvm info to the docs

README.md

@@ -184,6 +184,21 @@ it is already installed before enabling the bucket, otherwise you won't benefit
 from this plugin.
 
 
+#### RVM
+
+```ruby
+Vagrant.configure("2") do |config|
+  config.vm.box = 'some-box-with-ruby-installed'
+  config.cache.enable :rvm
+end
+```
+
+Compatible with probably with any type of linux guest distro, will hook into the `cache`
+folder under the result of running `rvm info` as the default SSH user (usualy
+`vagrant`) on your guest. If you use rvm on the guest machine, make sure
+it is already installed before enabling the bucket, otherwise you won't benefit
+from this plugin.
+
 ## Finding out disk space used by buckets
 
 _TODO_