Added feature table

Author: Nyholm

README.md

@@ -2,3 +2,12 @@
 [![Build Status](https://travis-ci.org/php-cache/array-adapter.svg?branch=master)](https://travis-ci.org/php-cache/array-adapter) [![codecov.io](https://codecov.io/github/php-cache/array-adapter/coverage.svg?branch=master)](https://codecov.io/github/php-cache/array-adapter?branch=master)
 
 This is a implementation for the PSR-6 for an array cache. This implementation supports tags. 
+
+This adapter could also be called Ephemeral or Memory adapter.  
+
+
+| Feature |   |
+| ------- | - | 
+| Flush everything | Yes 
+| Expiration time | No
+| Support for tags | Yes