Update README.md

Remove PHP 7 reference from README

Author: hfig

README.md

@@ -1,7 +1,7 @@
 # Hfig/MAPI
 
 ## Introduction
-``Hfig/MAPI`` is a PHP 7 library for reading and working with Microsoft Outlook/Exchange format email messages (``.msg`` files, aka MAPI documents).
+``Hfig/MAPI`` is a PHP library for reading and working with Microsoft Outlook/Exchange format email messages (``.msg`` files, aka MAPI documents).
 
 The library can parse MAPI documents, and programatically extract the properties and streams of the document.