Update MD doc for devs

docs/notes/development.md

@@ -12,13 +12,17 @@ You are welcome to contribute code using [GitHub pull requests](https://github.c
 
 > Before submitting a pull request, please make sure you've checked out the [Contribution Guidelines](https://github.com/pegjs/pegjs/blob/master/.github/CONTRIBUTING.md).
 
+_Ensure you have Node.js v6+ and Yarn installed._
+
 1. Create a fork of https://github.com/pegjs/pegjs
 2. Clone your fork, and optionally create a new branch
-3. Run the command `npm install` from the root of your clone
+3. Run the command `yarn install` from the root of your clone
 4. Add and commit your changes
 5. Validate your changes:
-    - Lint the JavaScript changes (command line only, run `gulp lint` or `npm run lint`)
-    - Run tests to ensure nothing's broken: [see separate documentation](https://github.com/pegjs/pegjs/blob/master/test/README.md)
+    - Lint the JavaScript changes (command line only, run `yarn lint`)
+    - Run tests to ensure nothing's broken: `yarn test` from the root of the repository
+    - Run benchmarks to check performance: `yarn benchmark`
+    - Check the impact of your commits: [see separate documentation](https://github.com/pegjs/pegjs/blob/master/tools/impact/README.md)
 6. If validation fails: reverse your commit, fix the problem and then add/commit again
 7. Push the commits from your clone to the fork
 8. From your fork, start a new pull request