Fix minor formatting issue

Author: ddevault

README.md

@@ -98,7 +98,7 @@ config.json.example to config.json in the config/ folder, and edit the following
 variables:
 
 * upstream_port: This is the port that Starbound will be running on. I recommend
-  21026. It **must** match the port in your starbound.config file.
+  `21026`. It **must** match the port in your starbound.config file.
 * upstream_hostname: Change this if you are hosting the wrapper on a different
   computer than your server.
 * bind_port: This should be 21025 normally; it is the port that StarryPy listens