Update readme to v0.7.0 (#83)

Author: flora-hofmann-frequenz

README.md

@@ -30,7 +30,7 @@ Please also refer to [examples](https://github.com/frequenz-floss/frequenz-clien
 
 ```bash
 # Choose the version you want to install
-VERSION=0.6.0
+VERSION=0.7.0
 pip install frequenz-client-reporting==$VERSION
 ```