README.md in rakuten_web_service-0.1.1 vs README.md in rakuten_web_service-0.2.0

@@ -4,11 +4,13 @@
 
 ## Installation
 
 Add this line to your application's Gemfile:
 
-    gem 'rakuten_web_service'
+```ruby
+  gem 'rakuten_web_service'
+```
 
 And then execute:
 
     $ bundle
 
@@ -16,10 +18,57 @@
 
     $ gem install rakuten_web_service
 
 ## Usage
 
-TODO: Write usage instructions here
+Now rakuten\_web\_service is supporting the following APIs: 
+
+* [Rakuten Ichiba Item Search API](http://webservice.rakuten.co.jp/api/ichibaitemsearch/)
+* [Rakuten Ichiba Genre Search API](http://webservice.rakuten.co.jp/api/ichibagenresearch/)
+* [Rakuten Ichiba Ranking API](http://webservice.rakuten.co.jp/api/ichibaitemranking/)
+
+### Configuration
+
+`RakutenWebService.configuration` allows you to specify your application's key called application\_id and your affiliate id(optional). 
+
+```ruby
+  RakutenWebService.configuration do |c|
+    c.application_id = YOUR_APPLICATION_ID
+    c.affiliate_id = YOUR_AFFILIATE_ID
+  end
+```
+
+### Search Ichiba Items
+
+```ruby
+  items = RakutenWebService::Ichiba::Item.search(:keyword => 'Ruby') # This returns Enamerable object
+  items.first(10).each do |item|
+    puts "#{item['itemName']}, #{item.price} yen" # You can refer to values as well as Hash. 
+  end
+```
+
+### Genre
+
+Genre class provides an interface to traverse sub genres.
+
+```ruby
+  root = RakutenWebService::Ichiba::Genre.root # root genre
+  # children returns sub genres
+  root.children.each do |child|
+    puts "[#{child.id}] #{child.name}"
+  end
+  
+  # Use genre id to fetch genre object
+  RakutenWebService::Ichiba::Genre[100316].name # => "水・ソフトドリンク"
+```
+
+
+### Ichiba Item Ranking
+
+```ruby
+  RakutenWebService::Ichiba::Item.ranking(:age => 30, :sex => 0) # returns the TOP 30 items for Male in 30s
+  RakutenWebService::Ichiba::Genre[100316].ranking # the TOP 30 items in "水・ソフトドリンク" genre
+```
 
 ## Contributing
 
 1. Fork it
 2. Create your feature branch (`git checkout -b my-new-feature`)