Update changelog

CHANGELOG.md

@@ -1,5 +1,13 @@
 ## [0.3.0](https://github.com/fgrehm/vagrant-cachier/compare/v0.2.0...master) (unreleased)
 
+BACKWARDS INCOMPATIBILITIES:
+
+  - Machine scoped cache dirs are now kept on `.vagrant/machines/MACHINE/cache`
+    to allow downloaded packages to be reused between providers. If a single cache
+    directory exists, the plugin will automatically move it to the right place,
+    if multiple directories are found, it will halt execution and will error out,
+    letting the user know what has to be done in order to fix things.
+
 FEATURES:
 
   - Add `file_cache_path` support for Chef. [GH-14]