README.md in stub_requests-0.1.2 vs README.md in stub_requests-0.1.3

@@ -12,24 +12,31 @@
 
 This is achieve by keeping a registry over the service endpoints.
 
 <!-- MarkdownTOC -->
 
+- [Required ruby version](#required-ruby-version)
 - [Installation](#installation)
 - [Usage](#usage)
   - [Register service endpoints](#register-service-endpoints)
   - [Stubbing service endpoints](#stubbing-service-endpoints)
   - [Metrics](#metrics)
+  - [Observing endpoint invocations](#observing-endpoint-invocations)
 - [Future Improvements](#future-improvements)
   - [API Client Gem](#api-client-gem)
 - [Development](#development)
 - [Contributing](#contributing)
 - [License](#license)
 - [Code of Conduct](#code-of-conduct)
 
 <!-- /MarkdownTOC -->
 
+<a id="required-ruby-version"></a>
+## Required ruby version
+
+Ruby version >= 2.3
+
 <a id="installation"></a>
 ## Installation
 
 Add this line to your application's Gemfile:
 
@@ -108,9 +115,29 @@
 
 ```ruby
 StubRequests.configure do |config|
   config.record_metrics = true
 end
+```
+
+<a id="observing-endpoint-invocations"></a>
+### Observing endpoint invocations
+
+```ruby
+# To jump into pry when a request is called
+callback = lambda do |request|
+  p request
+  binding.pry
+end
+
+callback = ->(request) { p request; binding.pry }
+
+StubRequests.subscribe_to(:document_service, :show, :get, callback)
+```
+
+```ruby
+# To unsubscribe from notifications
+StubRequests.unsubscribe_from(:document_service, :show, :get)
 ```
 
 <a id="future-improvements"></a>
 ## Future Improvements