README.md in rocketjob-2.1.3 vs README.md in rocketjob-3.0.0.alpha

@@ -15,9 +15,45 @@
 ## Support
 
 * Questions? Join the chat room on Gitter for [rocketjob support](https://gitter.im/rocketjob/support)
 * [Report bugs](https://github.com/rocketjob/rocketjob/issues)
 
+## Upgrading to V3
+
+* V3 replaces MongoMapper with Mongoid which supports the latest MongoDB Ruby client driver.
+* Replase usages of `rocket_job do` to set default values:
+
+~~~ruby
+  rocket_job do |job|
+    job.priority = 25
+  end
+~~~
+
+With:
+
+~~~ruby
+  self.priority = 25
+~~~
+
+* Replace `key` with `field` when adding attributes to a job:
+
+~~~ruby
+  key :inquiry_defaults, Hash
+~~~
+
+With:
+
+~~~ruby
+  field :inquiry_defaults, type: Hash, default: {}
+~~~
+
+* Replace usage of `public_rocket_job_properties` with the `user_editable` option:
+
+~~~ruby
+field :priority, type: Integer, default: 50, user_editable: true
+~~~
+
+
 ## Ruby Support
 
 Rocket Job is tested and supported on the following Ruby platforms:
 - Ruby 2.1, 2.2, 2.3, and above
 - JRuby 1.7.23, 9.0.5 and above