Add README.md file containing instructions on Ruby petstore sample

samples/client/petstore/ruby/README.md

@@ -0,0 +1,57 @@
+## Installation
+
+### Build a gem
+
+You can build the generated client into a gem:
+
+```shell
+gem build swagger-client.gemspec
+```
+
+Then you can either install the gem:
+
+```shell
+gem install ./swagger-client-4.06.08.gem
+```
+
+or publish the gem to a gem server like [RubyGems](https://rubygems.org/).
+
+Finally add this to your Gemfile:
+
+    gem 'swagger-client', '~> 4.06.08'
+
+### Host as a git repository
+
+You can also choose to host the generated client as a git repository, e.g. on github:
+https://github.com/xhh/swagger-petstore-ruby
+
+Then you can reference it in Gemfile:
+
+    gem 'swagger-client', :git => 'https://github.com/xhh/swagger-petstore-ruby.git'
+
+### Use without installation
+
+You can also use the client directly like this:
+
+```shell
+ruby -Ilib script.rb
+```
+
+## Configuration
+
+```ruby
+require 'swagger-client'
+
+Swagger.configure do |config|
+  config.api_key = 'special-key'
+  config.host = 'petstore.swagger.io'
+  config.base_path = '/v2'
+end
+```
+
+## Getting Started
+
+```ruby
+pet = PetApi.getPetById(5)
+puts pet.to_body
+```