Update library to use 7.0 and above

Author: unicodeveloper

README.md

@@ -12,7 +12,7 @@
 
 ## Installation
 
-[PHP](https://php.net) 5.4+ or [HHVM](http://hhvm.com) 3.3+, and [Composer](https://getcomposer.org) are required.
+[PHP](https://php.net) 7.0+ or [HHVM](http://hhvm.com) 3.3+, and [Composer](https://getcomposer.org) are required.
 
 To get the latest version of jusibe-php-lib, simply add the following line to the require block of your `composer.json` file.