update README

README.md

@@ -8,7 +8,7 @@ docker run -d --name rocksdb-prometheus-exporter \
   -p 8080:8080 \
   -v <path(s) to stores on host>:/stores:ro \
   -e "PATHS=/stores/*/*/*" \
-  <registry>/rocksdb-prometheus-exporter:<version>
+  vouchio/rocksdb-prometheus-exporter
 ```
 
 As you can see, `$PATHS` can be a glob which gets expanded internally. This lets you specify multiple stores to monitor. The stores are mounted readonly (using `:ro`) to ensure we don't accidentally corrupt any stores.