Update README with more dev instructions

README.md

@@ -26,7 +26,18 @@ for my own convenience:
 5. `virtualenv lib` # make a python virtualenv
 6. `lib/bin/pip install -r requirements.txt`
 
-TODO: Can this be streamlined? Maybe move Makefile commands into `npm` commands.
+## Development
+
+`npm run watch` will use nodemon to restart the server when any file changes.
+
+Dummy versions of `mpg321` and the tag reader are available in the `bin`
+directory. These are node scripts, so you would include them in your
+`config.json` like so:
+
+    {
+        "tag_reader": ["node", "./bin/tag-reader-dummy"],
+        "mpg321": ["node", "./bin/mpg321-dummy"]
+    }
 
 ## config.json