Add CoolSMS PHP SDK, and update Composer dependencies

vendor/coolsms/php-sdk/README.md

@@ -0,0 +1,26 @@
+# Coolsms PHP SDK
+
+Send Message & Alimtalk using PHP and REST API.
+
+## Installation
+
+- The recommended way to install Coolsms PHP SDK is through composer:
+
+  ```bash
+  $ composer require coolsms/php-sdk
+  ```
+
+- Package install url ( source code & examples ) : http://www.coolsms.co.kr/download/3130218
+
+- Github : https://github.com/coolsms/php-sdk
+
+## Requirements
+
+* PHP 5.5 or greater
+* Composer
+* PHP CURL extension
+* PHP JSON extension
+
+## Usage
+
+Look at the 'http://www.coolsms.co.kr/PHP_SDK_Example'.