Installation instructions and usage example

Author: WyriHaximus

Diff for: README.md

@@ -1,4 +1,4 @@
-# API Client PSR-7 Oauth1
+# PSR-7 Oauth1 request signer
 
 [![Build Status](https://travis-ci.org/php-api-clients/psr7-oauth1.svg?branch=master)](https://travis-ci.org/php-api-clients/psr7-oauth1)
 [![Latest Stable Version](https://poser.pugx.org/api-clients/psr7-oauth1/v/stable.png)](https://packagist.org/packages/api-clients/psr7-oauth1)
@@ -7,6 +7,36 @@
 [![License](https://poser.pugx.org/api-clients/psr7-oauth1/license.png)](https://packagist.org/packages/api-clients/psr7-oauth1)
 [![PHP 7 ready](http://php7ready.timesplinter.ch/php-api-clients/psr7-oauth1/badge.svg)](https://appveyor-ci.org/php-api-clients/psr7-oauth1)
 
+# Installation
+
+To install via [Composer](http://getcomposer.org/), use the command below, it will automatically detect the latest version and bind it with `^`.
+
+```bash
+composer require api-clients/psr7-oauth1 
+```
+
+# Example
+
+```php
+<?php
+
+$requestSigner = new RequestSigner(
+    new ConsumerKey('consumer_key'),
+    new ConsumerSecret('consumer_secret')
+);
+
+// Returns a signed PSR7 request you can use in any PSR7 capable HTTP client
+$request = $requestSigner->withAccessToken(
+    new AccessToken('token_key'),
+    new TokenSecret('token_secret')
+)->sign($request);
+```
+
+
+# Contributing
+
+Please see [CONTRIBUTING](CONTRIBUTING.md) for details.
+
 # License
 
 The MIT License (MIT)