Added supported versions to the README

Author: thinkingserious

CONTRIBUTING.md

@@ -64,7 +64,7 @@ We welcome direct contributions to the ruby-http-client code base. Thank you!
 
 ##### Prerequisites #####
 
-- Ruby 2.2 or higher
+- Ruby version 2.2
 
 ##### Initial setup: #####
 

README.md

@@ -10,14 +10,16 @@ All updates to this library is documented in our [CHANGELOG](https://github.com/
 
 # Installation
 
+## Prerequisites
+
+- Ruby version 2.2
+
+## Install Package
+
 ```bash
 gem install ruby_http_client
 ```
 
-## Dependencies
-
-- Ruby 2.2 or higher
-
 # Quick Start
 
 `GET /your/api/{param}/call`