Review feedback.

docs/contributing.rst

@@ -39,6 +39,7 @@ Then in each shell where you're working on the client, do:
 .. code-block:: shell
 
    source ./venv/bin/activate
+   export SERVER=https://acme-staging.api.letsencrypt.org/directory
    source tests/integration/_common.sh
 
 After that, your shell will be using the virtual environment, and you run the
@@ -116,6 +117,14 @@ and working. Fetch and start Boulder using:
 If you have problems with Docker, you may want to try `removing all containers and
 volumes`_ and making sure you have at least 1GB of memory.
 
+Set up a certbot_test alias that enables easily running against the local
+Boulder:
+
+.. code-block:: shell
+
+   export SERVER=http://localhost:4000/directory
+   source tests/integration/_common.sh
+
 Run the integration tests using:
 
 .. code-block:: shell