Link to code review guideline in dev workflow

Author: lukpueh

dev-workflow.md

@@ -63,5 +63,5 @@ your pull request, look through the output and see if you can fix the problems.
 You can also run tests locally!  Check the `.travis.yml` or `appveyor.yml` files
 to see what commands the build systems run.
 
-1. **Request a review**. You can request reviews directly in *GitHub*. Also,
-don't be afraid to re-ask if no one has been on it after a couple of days.
+1. **Request a code review**. See our [code review guidelines](code-review.md)
+   for more details.