Add note on running acceptance tests to README

services/docstore/README.md

@@ -5,6 +5,13 @@ A CRUD API for storing and updating text documents in projects
 
 [![Build Status](https://travis-ci.org/sharelatex/docstore-sharelatex.png?branch=master)](https://travis-ci.org/sharelatex/docstore-sharelatex)
 
+Acceptance tests can be run with the command
+```
+docker run --rm -e AWS_BUCKET="<bucket-name>" -e AWS_ACCESS_KEY_ID=<aws-access-key> -e AWS_SECRET_ACCESS_KEY=<aws-secret-access-key> -v $(pwd):/app sharelatex/acceptance-test-runner
+```
+where `bucket-name`, `aws-access-key` and `aws-secret-access-key` are the credentials for an AWS S3 bucket.
+
+
 License
 -------