Update CHANGELOG + README as per #397 [ci skip]

CHANGELOG.md

@@ -5,6 +5,11 @@
 
 ## 3.0.3
 
+##### Breaking Change: If you use a custom initializer for PaperTrail in conjunction with Rails, you will need to add this line of code to the beginning of it:
+```ruby
+PaperTrail::Rails::Engine.eager_load!
+```
+
   - [#386](https://github.com/airblade/paper_trail/issues/386) - Fix eager loading of `versions` association with custom class name
     in `ActiveRecord` 4.1.
   - [#384](https://github.com/airblade/paper_trail/issues/384) - Fix `VersionConcern#originator` instance method.

README.md

@@ -481,6 +481,10 @@ You can avoid having to do this manually by setting your initializer to pick up
 
 ```ruby
 # config/initializers/paper_trail.rb
+
+# the following line is required for PaperTrail >= 3.0.3 with Rails
+PaperTrail::Rails::Engine.eager_load!
+
 if defined?(::Rails::Console)
   PaperTrail.whodunnit = "#{`whoami`.strip}: console"
 elsif File.basename($0) == "rake"
@@ -556,6 +560,11 @@ If you only use custom version classes and don't use PaperTrail's built-in one,
 - either declare the `PaperTrail::Version` class to be abstract like this (in an initializer):
 
 ```ruby
+# config/initializers/paper_trail.rb
+
+# the following line is required for PaperTrail >= 3.0.3 with Rails
+PaperTrail::Rails::Engine.eager_load!
+
 PaperTrail::Version.module_eval do
   self.abstract_class = true
 end