Added feature table

Author: Nyholm

README.md

@@ -1,4 +1,11 @@
 # Filesystem PSR-6 adapter 
 [![Build Status](https://travis-ci.org/php-cache/filesystem-adapter.svg?branch=master)](https://travis-ci.org/php-cache/filesystem-adapter) [![codecov.io](https://codecov.io/github/php-cache/filesystem-adapter/coverage.svg?branch=master)](https://codecov.io/github/php-cache/filesystem-adapter?branch=master)
 
-This is a implementation for the PSR-6 for an filesystem cache. This implementation supports tags. 
+This is a implementation for the PSR-6 for a filesystem cache. This implementation supports tags. This adapter 
+required [Flysystem](http://flysystem.thephpleague.com/).
+
+| Feature |   |
+| ------- | - | 
+| Flush everything | Yes 
+| Expiration time | Yes
+| Support for tags | Yes