Add the credits section

Author: dspasic

Diff for: README.md

@@ -22,3 +22,7 @@ You can contribute in one of three ways:
 3. Contribute new features or update the wiki.
 
 > The code contribution process is not very formal. You just need to make sure that you follow the PSR-0, PSR-1, and PSR-2 coding guidelines. Any new code contributions must be accompanied by unit tests where applicable.
+
+# Credits
+
+The dashboard is a fork of the project [rlerdorf/opcache-status](https://github.com/rlerdorf/opcache-status).