Merge pull request #12 from takachin/4.8

fixed installation manual

Author: nanasess

README.md

@@ -16,7 +16,7 @@ You may use [Composer](https://getcomposer.org/) to download and install PHPUnit
 
 ```sh
 $ cd path/to/your/php-project
-$ composer require --dev php5friends/phpunit
+$ composer require --dev php5friends/phpunit48
 ```
 
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