README.md: update minio mint test steps

these have changed recently, but the docs were slightly out of date.

Change-Id: Iea100aaaa56076ad2b7013ca0eae52c36605d7f6

README.md

@@ -40,16 +40,19 @@ The following S3 methods are supported:
 - ListObjects
 - ListObjectsV2
 
-We use the minio mint testsuite to ensure our compatibility to the S3 API. As some S3 methods are not supported yet, we use a custom build that you can run it against any endpoint using docker.
-To build our custom image and tag it as storj/mint:
-```
-docker build --pull https://github.com/storj/minio.git#storj -f Dockerfile.mint -t storj/mint
-```
-To run the tests against the endpoint `endpoint_address` (using the `HOST:PORT` format), use:
+We run a fork of the minio/mint repository at [storj/gateway-mint](https://github.com/storj/gateway-mint/)
+used to test correctness of the gateway.
+
+To run the tests:
+
 ```
-docker run -e SERVER_ENDPOINT=endpoint_address -e ACCESS_KEY=myaccesskey -e SECRET_KEY=mysecretkey -e ENABLE_HTTPS=0 storj/mint
+docker run --rm \
+	-e SERVER_ENDPOINT=endpoint_address \
+	-e ACCESS_KEY=myaccesskey \
+	-e SECRET_KEY=mysecretkey \
+	-e ENABLE_HTTPS=0 \
+	storjlabs/gateway-mint
 ```
-The `ENABLE_HTTPS` flag indicates if https should be used (`ENABLE_HTTPS=1`)
 
 # License