README.md in disco-0.2.0 vs README.md in disco-0.2.1

@@ -1,8 +1,8 @@
 # Disco
 
-:fire: Collaborative filtering for Ruby
+:fire: Recommendations for Ruby and Rails using collaborative filtering
 
 - Supports user-based and item-based recommendations
 - Works with explicit and implicit feedback
 - Uses high-performance matrix factorization
 
@@ -99,11 +99,12 @@
 [Ahoy](https://github.com/ankane/ahoy) is a great source for implicit feedback
 
 ```ruby
 views = Ahoy::Event.
   where(name: "Viewed post").
-  group(:user_id, "properties->>'post_id'"). # postgres syntax
+  group(:user_id).
+  group("properties->>'post_id'"). # postgres syntax
   count
 
 data =
   views.map do |(user_id, post_id), count|
     {
@@ -313,5 +314,14 @@
 
 - [Report bugs](https://github.com/ankane/disco/issues)
 - Fix bugs and [submit pull requests](https://github.com/ankane/disco/pulls)
 - Write, clarify, or fix documentation
 - Suggest or add new features
+
+To get started with development:
+
+```sh
+git clone https://github.com/ankane/disco.git
+cd disco
+bundle install
+bundle exec rake test
+```