Fix aggregate_root dependency lookup

Author: fidel

rails_event_store-browser/Gemfile

@@ -4,3 +4,4 @@ gemspec
 gem 'rails_event_store', path: '../rails_event_store'
 gem 'ruby_event_store',  path: '../ruby_event_store'
 gem 'rails_event_store_active_record', path: '../rails_event_store_active_record'
+gem 'aggregate_root', path: '../aggregate_root'