Update readme to display current version number

Author: jeskew

README.md

@@ -15,7 +15,7 @@ requiring the`aws/aws-sdk-php-symfony` package in your project's `composer.json`
 ```json
 {
  "require": {
- "aws/aws-sdk-php-symfony": "~0.1"
+ "aws/aws-sdk-php-symfony": "~1.0"
  }
 }
 ```