Remove circle CI status (we're not using that any more)

Author: martinthomson

README.md

@@ -1,7 +1,5 @@
 # Encryped Content-Encoding for HTTP
 
-[![CircleCI](https://circleci.com/gh/web-push-libs/encrypted-content-encoding/tree/master.svg?style=svg)](https://circleci.com/gh/web-push-libs/encrypted-content-encoding/tree/master)
-
 nodejs and python implementations are available.
 
 ```sh