update readme

Author: MagicalTux

README.md

@@ -1,7 +1,12 @@
-# libgit2 wrapper for PHP
+# libgit2 bindings for PHP 7
 
 Because I need libgit2 and the implementation at https://github.com/libgit2/libgit2 is not maintained anymore (and no PHP7 implementation currently exists) I decided to put one together quickly.
 
 This implementation __requires__ PHP7 and implements classes unlike the libgit2 version, because it makes more sense.
 
 Work in progress. Methods I need will be implemented first.
+
+## Requirements
+
+PHP 7.0 or above.
+